The Annals of Cambria (The Welsh Annals) (900's):
539 A.D.: The Battle of Camlann, in which Arthur and Medraut both fell; and there was widespread death in Britain and in Ireland.
William of Malmesbury, The Deeds of the English Kings (1125):
"However, the tomb of Arthur is nowhere to be found--that man whose second coming has been hymned in the dirges of old. Yet the sepulcher of Walwen [Gawain] . . . is fourteen feet long. It is said by some that Walwen's body was cast up from a shipwreck after he had been wounded by his enemies, while others say that he was murdered by his felow citizens at a public feast. And so the truth lies in doubt, though neither story would lessen the assertion of his fame."
Gerald of Wales [Giraldus Cambrensis]: On the Instruction of Princes (1190's):
"Then Arthur's body, which legends have fancifully treated as being phantomlike at its end and carried away by spirits to a far off place where it is immune to death, was discovered in these days of ours, buried deep in the earth . . . in a holy burial ground at Glastonbury. . . . I myself have seen this, and I have traced the letters engraved on the cross, which do not project forward but rather inwardly toward the stone: 'Here lies buried the famous King Arthur with Guinevere his second wife on the Isle of Avalon.'"
Geoffrey of Monmouth, The History of the Kings of Britain: (ca. 1134):
"Arthur himself, our renowned King, was mortally wounded and was carried off to the Isle of Avalon, so that his wounds might be attended to. He handed the crown of Britain over to his cousin Constantine, the sone of Cador Duke of Cornwall: this in the year 542 after our Lord's Incarnation" (Lewis Thorpe, trans. Penguin Classics, p. 261).
Wace, Le Roman de Brut: (ca. 1155):
"Arthur, if the chronicle is true, received a mortal wound to his body. He had himself carried to Avalon, for the treatment of his wounds. He is still there, awaited by the Britons, as they say and believe, and will return and may live again. Master Wace, who made this book, will say no more of his end than the prophet Merlin did. Merlin said of Arthur, rightly, that his death would be doubtful. The prophet spoke truly: ever since, people have always doubted it and always will, I think, doubt whether he is dead or alive. Truly, 542 years after the Incarnation he did have himself carried to Avalon. It was a great loss that he had no children. To Cador's son, Costentin of Cornwall, his cousin, he surrendered his kingdom, and told him to be king until he returned." (Judith Weiss, trans. Everyman Library, 1997, p. 102)
The Death of King Arthur (La Mort Artu), in the Vulgate Cycle (ca. 1230):
"He [Girflet] looked back to where he had left the king, and saw a ship entirely occupied by women coming across the sea. When the ship had come to the shore opposite where Arthur was, they came to the side, and their lady, who was holding King Arthur's sister Morgan by the hand, called to Arthur to come aboard. As soon as Arthur saw his sister Morgan, he arose from the ground where he was sitting, and went aboard the ship, taking his horse and his arms with him. . . .
"In a short time, the ship travelled from the shore more than eight times the distance one can shoot from a crossbow. . . .
"On the third day, he departed and decided to go to the Black Chapel . . . Before the altar he saw two rich and beautiful tombs, but one of them was far richer and more beautiful than the other. . . On the very splendid and rich tomb there was written:
'Here Lies King Arthur Who Through His Valor Conquered Twelve Kingdoms.'"
(James Cable, trans. Penguin Editions, pp. 224-225)
The Death of Arthur, in the Post-Vulgate: (ca. 1235-1240):
"He [Girflet] had not stood there long when he saw coming across the sea a little bark in which there were many ladies. The bark landed near King Arthur, and the ladies emerged and went to the king. Among them was Morgan the Enchantress, King Arthur's sister . . . and entreated him to come on board the bark. After he was on board, she had his horse and all his armor put aboard; then the bark began to go across the sea with him and with the ladies, so that no knight or anyone else in the kingdom of Logres might say with certainty that he had seen King Arthur afterward. . . .
"On the third day, he left and went to the Ancient Chapel . . . He . . . found two rich, beautiful tombstones. . . . On the other, marvelously rich one, there were letters that said: Here lies King Arthur, who by his prowess and ability conquered twelve kingdoms. . . .
[Girflet swoons, and when he comes to, he asks if it is true that King Arthur is buried in this place. The 'good man' tells him it is true. ]
"Then Girflet went to the tomb, with the good man standing nearby. He raised the stone, and when he looked inside he saw nothing except King Arthur's helmet, the very one he had worn in the dolorous battle. . . .
"So in vain I will labor to find out how King Arthur died. Truly he's the mysterious king, whose death no man shall know, and he certainly told the truth that just as he came to the kingdom of Logres in mystery, so has he gone away from it in mystery. But since I see that there's no point in my seeking him, as he can't be found, I'll never live in the world again."
(Martha Asher, trans. in Lancelot-Grail, the Old French Arthurian Vulgate and Post-Vulgate Translation, Vol. 5, Garland, p.307).
Thomas Malory, Le Morte Darthur: (ca. 1468-1470):
"Yet some men say in many parts of England that King Arthur is not dead, but had by the will of our Lord Jesu into another place; and men say that he shall come again, and he shall win the holy cross. I will not say it shall be so, but rather I will say: here in this world he changed his life. But many men say that there is written upon his tomb this verse:
Hic iacet Arthurus, Rex quondam, Rexque futurus."
(Wordsworth Classics, Tom Griffith, gen. ed., p. 794)