Navigatio Sancti Brendani
Navigatio Sancti Brendani (abbatis) ("The Sea Journey [of the Abbot] Saint Brendan") is the title of an immram (mythical travel story) that probably originated in the 9th century from the combination of Celtic legends and Christian ideas. Since the 12th century, this story, translated into some languages, has been widely distributed throughout Europe. According to research by the American scholar Carl Selmer, a total of around 120 versions have been preserved.
The Navigatio Sancti Brendani, which he is said to have made with twelve companions between 565 and 573, describes his journey into the Atlantic Ocean from Ireland with a curragh. He wanted to reach the "Terra Repromissionis", a promised island in the west. On the way to this Brendan Island, which is listed in several medieval maps, he experiences many adventures, which are recorded in 29 chapters.
After the construction of the boat on Saint-Enda Island (Inishmore, Aran Islands) they sail out to the open sea, where after a few days they land on an island that turns out to be the largest fish in the world, called Jasconius. They also discover the Monk's Island, The Sheep Island and the Bird Island, where they meet a mysterious companion, the Procurator (referred to in the English translations as a steward), who now supplies them with food and drink and shows them the way. He tells them that they would have to go to these islands for seven years. They watch the battle of two sea monsters, are attacked by the bird Greif, come to a floating crystal pillar (an iceberg?),are expelled by the inhabitants of the volcanic island with glowing slag stones and drive through the "wild sea"(drift ice?). Eventually they find the island of the blessed, stay there for some time and then return to Ireland. Saint Brendan tells all the confreres the adventures they have experienced and prophesies his imminent death, which then also occurs. 
Timothy Severin's Journey
The Navigatio Sancti Brendani probably played a role in the discovery of America. It is to be assumed that Christopher Columbus also knew the mythical travelogue about the Western Journey of the Irish monk Brendan, which was popular since the Middle Ages. The historian and writer Tim Severin proved with a curragh in 1977 that the journey of Saint Brendan to North America was possible, as can be interpreted from the Navigatio Sancti Brendani.  On May 16 (St. Brendan's Name Day) in 1976, he launched a repeat of the Navigatiowith the perfect replica of an Irish leather curragh called Brendan from the mouth of The Irish Brandon Creek (County Kerry). With some companions he sailed through the North Atlantic in two stages – with a winter break in Iceland. On June 25, 1977, they landed at Musgrave Harbor on Newfoundland. His travelogue is reminiscent of the books of Thor Heyerdahl (Kon-Tiki and Ra).
Here is the Translated Voyage of Saint Brendan in it's entirety.
Navigatio sancti Brendani abbatis[the Voyage of St Brendan the Abbot]Source: Edition by Archbishop P. F. MoranTranslator: Denis O’DonoghuePublished: D. O’Donoghue, Brendaniana Date of Translation: 1893St Brendan, son of Finnlug Ua Alta, of the race of Eoghan, was born in the marshy district of Munster He was famed for his great abstinence and his many virtues, and was the patriarch of nearly three thousand monks. While he was in his spiritual war–fare, at a place called Ardfert-Brendan there came to him one evening, a certain father, named Barinthus, of the race of King Niall, who, when questioned by St Brendan, in frequent converse, could only weep, and cast himself prostrate, and continue the longer in prayer; but Brendan raising him up, em–braced him, saying: ‘Father, why should we be thus grieved on the occasion of your visit? Have you not come to give us comfort? You ought, indeed, make better cheer for the brethren. In God’s name, make known to us the divine secrets, and refresh our souls by recounting to us the various wonders you have seen upon the great ocean.’ Then Barinthus, in reply, proceeds to tell of a certain island: ‘My dear child, Mernoc, the guardian of the poor of Christ, had fled away from me to become a solitary, and found, nigh unto the Stone mountain, an island full of delights. After some time I learned that he had many monks there in his charge, and that God had worked through him many marvels. I, therefore, went to visit him, and when I had approached within three days’ journey, he, with some of the brethren, came out to meet me, for God had revealed to him my advent. As we sailed unto the island the brethren came forth from their cells towards us, like a swarm of bees, for they dwelt apart from each other, though their intercourse was of one accord, well grounded in faith, hope, and charity; one refectory; one church for all, wherein to-discharge the divine offices. No food was served but fruits and nuts, roots and vegetables of other kinds. The brethren, after compline, passed the night in their respective cells until the cock-crow, or the bell tolled for prayer. When my dear son and I had traversed the island, he led me to the western shore, where there was a small boat, and he then said: ‘Father, enter this boat, and’ we will sail on to the west, towards the island called the Land of Promise of the Saints, which God will grant to those who succeed us in the latter days.’–When we entered the boat and set sail, clouds over–shadowed us on every side, so dense that we could scarcely see the prow or the stern of the boat. After the lapse of an hour or so, a great light shone around us, and land appeared, spacious and grassy, and bearing all manner of fruits. And when the boat touched the shore; we landed, and walked round about the island for fifteen days, yet could not reach the limits thereof. No plant saw we there without its flower; no tree without its fruit; and all the stones thereon were pre–cious gems. But on the fifteenth day we discovered a river flowing from the west towards the east, when, being at a loss what to do, though we wished to cross over the river, we awaited the direction of the Lord. While we thus considered the matter, there appeared suddenly before us a certain man, shining with a great light, who, calling us by our names, addressed us thus’: ‘Welcome, worthy brothers, for the Lord has revealed to yon the land He will grant unto His saints. There is one-half of the island up to this river, which you are not permitted to pass over; return, therefore, whence you came’ .When he had ceased to speak, we asked him his name, and whence he had come. But he said: 'Why do you ask these questions? Should you not rather inquire about this island. Such as you see it now, so has it continued from the beginning of the world. Do you now need food or drink? Have you been weighed down by sleep, or shrouded in the darkness of the night I Know then for certain that here it is for ever day, without a shadow of darkness, for the Lord Jesus Christ is the light thereof, and if men had not trans–gressed the commandment of God, in this land of delights would they have always dwelt.’Hearing this we were moved to tears, and having rested awhile, we set out on our return journey, the man aforesaid accompanying us to the shore, where our boat was moored. When we had entered the boat, this man was taken from our sight, and we went on into the thick darkness we had passed through before, and thus unto the Island of delights. But when the brethren there saw us, they rejoiced with great joy at our return, as they had long bewailed our absence, and they said: ‘Why, O fathers, did you leave us, your little
flock, to stray without a shepherd in the wilderness? We knew, indeed, that our abbot frequently departed somewhere from us, and remained away sometimes a month, sometimes a fortnight, or a week more or less.When I heard this I tried to console them, and said: ‘Brethren, harbour no thought of evil, for your lives here are certainly passed at the very portals of paradise. Not far away from you lies the island, called the ‘Land of Promise of the Saints,’ where night never falls nor day closes; thither your abbot, Mernoc, resorts, as the angels of God watch over it. Do you not know, by the fragrance of our garments, that we have been in the paradise of God?’. They replied: ‘Yes, father, we knew well that you had been in the paradise of God, for we often found this fragrance from the garments of our abbot, which lingered about us for nearly forty days.’ I then told them that I had abided therein with my dear son, for a fortnight, without food or drink; yet, so complete was our’ bodily refreshment, that we would ‘seem to others to have been filled to repletion. ‘When forty days had passed, having received the bless–ings of the abbot and the brethren, I came away with my companions, that I may return to my little cell to which I will go on to-morrow.Having heard all this, St Brendan and his brethren cast themselves on the ground, giving glory to God in these words: ‘Righteous Thou art, O Lord, in all Thy ways, and holy in all Thy works, who hast revealed to Thy children so many and so great wonders; and blessed be Thou for Thy gifts, who hast this day refreshed, us all with this spiritual repast,’ ‘When these discourses were ended, St Brendan said: ‘Let us now proceed to the refection of the body, and the new command–ment’. The night having passed, St Barinthus, receiving the blessing of the brethren, returned to his own cell.IISt Brendan soon after selected from his whole community fourteen monks. Taking these apart, the venerable father Brendan retired with them into an oratory where he thus addressed them: ‘Dearly beloved fellow-soldiers of mine, I request your advice and assistance, for my heart and mind are firmly set upon one desire; if it be only God’s holy will, I have in my heart resolved to go forth in quest of the Land of Promise of the Saints, about which Father Barinthus discoursed to us. What do you think? What is your advice?’ But they, well knowing the purpose of their holy father, replied, as with one voice: ‘Father-abbot, your will is our will also. Have we not forsaken our parents? Have we not slighted our family prospects? Have we not committed into your hands even our very bodies? We are, therefore, ready to go with you, whether unto life or unto death, provided only we find such to be the will of God.’IIISt Brendan and the chosen brethren then decided to make a fast of forty days, at three days’ intervals, and afterwards to take their departure. Those forty days having elapsed, St Brendan, affectionately taking leave of his monks, and commending them to the special care of the Prior of his monastery, who was afterwards his successor there, sailed forth towards the west, with fourteen brethren, to the island wherein dwelt St Enda, and remained there three days and three nights.IVHaving received the blessing of this holy father and all his monks, he proceeded to the remotest part of his own country, where his parents abode. However, he willed not to visit them, but went up to the summit of the mountain there, which extends far into the ocean, on which is ‘St Brendan’s Seat;’ and there he fitted up a tent, near a narrow creek, where a boat could enter. Then St Brendan and his companions, using iron implements, prepared a light vessel, with wicker sides and ribs, such as is usually made in that country, and covered it with cow-hide, tanned in oak-bark, tarring the joints thereof, and put on board provisions for forty days, with butter enough to dress hides for covering the boat and all utensils needed for the use of the crew.He then ordered the monks to embark, in the name of the Father, and of the Son, and of the Holy Ghost.IVBut while he stood on the shore and blessed the little creek, behold three more monks from his monastery came up, and cast themselves at his feet, saying: ‘O dearest father, suffer us, for the love of Christ, to accompany you on your voyage, otherwise we will die hereof hunger and thirst, for we are resolved to travel with thee all the days of our lives.’ When the man of God saw their great urgency, he ordered them to embark, saying: ‘Have your will, my children;’ but adding: ‘I know well why you have come hither. One of you has acted well, for God had provided for him an excellent place; but for two others, He has appointed harm and judgment.’
St Brendan then embarked, and they set sail towards the summer solstice. They had a fair wind, and therefore no labour, only to keep the sails properly set; but after twelve days the wind fell to a dead calm, and they had to labour at the oars until their strength was nearly exhausted. Then St Brendan would encourage and exhort them: ‘Fear not, brothers, for our God will be unto us a helper, a mariner, and a pilot; take in the oars and helm, keep the sails set, and may God do unto us, His servants and His little vessel, as He willeth.’. They took refreshment always in the evening, and sometimes a wind sprung up; but they knew not from what point it blew, nor in what direction they were sailing.At the end of forty days, when all their provisions were spent, there appeared towards the north, an island very rocky and steep. When they drew near it, they saw its cliffs upright like a wall, and many streams of water rushing down into the sea from the summit of the island; but they could not discover a landing-place for the boat. Being sorely distressed with hunger and thirst, the brethren got some vessels in which to catch the water as it fell; but St Brendan cautioned them: ‘Brothers! do not a foolish thing; while God wills not to show us a landing-place, you would take this without His permission; but after three days the Lord Jesus Christ will show His servants a secure harbour and resting-place, where you ‘may refresh your wearied bodies.’When they had sailed round the island for three days, they descried, on the third day, about the hour of none, a small cove, where the boat could enter; and St Brendan forthwith arose and blessed this landing-place, where the rocks stood on every side, of wonderful steepness like a wall. When all had disembarked and stood upon the beach, St Brendan directed them to remove nothing from the boat, and then there appeared a dog, approaching from a bye-path, who came to fawn upon the saint, as dogs are wont to fawn upon their masters. ‘Has not the Lord,’ said St Brendan, ‘sent us a goodly messenger; let us follow him;’ and the brethren followed the dog, until they came to a large mansion, in which they found a spacious hall, laid out with couches and seats, and water for washing their feet, ‘When they had taken some rest, St, Brendan warned them thus: ‘Beware lest Satan lead you into temptation, for I can see him urging one of the three monks, who followed after us from the monastery, to a wicked theft. Pray you for his soul, for his flesh is in Satan’s power.’The mansion where they abode had its walls hung around with vessels made of various metals, with bridle-–bits and horns inlaid with silver,St Brendan ordered the serving brother to produce the meal which God had sent them; and without delay the table was laid with napkins, and with white loaves and fish for each brother, When all had been laid out, St Brendan blessed the repast and the brethren: ‘Let us give praise to the God of heaven, who provideth food for all His creatures.’ Then the brethren partook of the repast, giving thanks to the Lord, and took likewise drink, as much as they pleased. The meal. being finished, and the divine office discharged, St Brendan said: ‘Go to your rest now; here you see couches well dressed for each of you; and you need to rest those limbs over-wearied by your labours during our voyage. ‘When the brethren had gone to sleep, St Brendan saw the demon, in the guise of a little black boy, at his work, having in his hands a bridle-bit, and beckoning to the monk before mentioned: then he rose from his couch, and remained all night in prayer.When morning came the brethren hastened to per–form the divine offices, and wishing to take to their boat again, they found the table laid for their meal. as on the previous day; and so for three days and nights did God provide their repasts for His servants.VIIAfterwards St Brendan set out on his journey with the brethren, first cautioning them not to take away any property from the island. ‘God forbid,’ said they, ‘that any of us should dishonour our journey by theft;’ whereupon St Brendan said: ‘Behold the brother of whom I spoke to yon on yesterday has concealed in his bosom a silver bridle–-bit which the devil gave him last night.’ When the brother in question heard this he cast away the bridle-bit out of his. bosom, and fell at the feet of the saint, crying aloud: ‘O father, I am guilty: forgive me, and pray that my soul may not be lost’ and all the brethren cast themselves on the ground, earnestly beseeching the Lord for his soul’s sake. When they rose from the ground, and St Brendan had raised up the guilty brother, they all saw a little black boy leap out of his bosom, howling loudly: ‘Why, O man of God, do you expel me from my abode, where I have dwelt for seven years, and drive me away, as a stranger, from my secure posses–sion? Then St Brendan said: ‘I command thee, in the name of the Lord Jesus Christ, that thou injure no man until the day of judgment’ and turning to the penitent brother, he told