When Percivale beheld that horse he marvelled that it was so great and so well apparelled; and not for then he was so hardy, and he leapt upon him, and took none heed of himself. And so anon as he was upon him he thrust to him with his spurs, and so he rode by a forest, and the moon shone clear. And within an hour and less he bare him four days’ journey thence, until he came to a rough water the which roared, and his horse would have borne him into it.

And when Sir Percivale came nigh the brim, and saw the water so boistous, he doubted to overpass it. And then he made a sign of the cross in his forehead. When the fiend felt him so charged he shook off Sir Percivale, and he went into the water crying and roaring, making great sorrow, and it seemed unto him that the water brent.

Malory's Le Morte d'Arthur