The Tale of Taliesin by E.M. Wilmot-Buxton

Tegid Voel and Caridwen his wife lived on an island in the midst of Lake Tegid. (Nowadays the lake is called Bala, and there is no island to be seen.) They had an elder son, a fair and comely youth, and a very beautiful daughter; but their youngest son was uglier than anyone in the whole world. This troubled his mother Caridwen at first; but she said to herself: "If he cannot be handsome, he shall, at anyrate, be very learned. " Now, Caridwen was a witch, so she set to work to boil a Cauldron of Knowledge, of which the boiling must not cease for a year and a day. At the end of that time it would yield three drops of precious liquid, which would make whoever drank it wise for the rest of his life. She set Gwion Bach, who was passing by, to stir the cauldron, and a blind man named Morda to keep up the fire underneath; but, fearing that Gwion Bach had seen what she put into the cauldron, and would tell her secrets to others, she made up her mind to kill him directly he had done his work for her.

Now, one day, as the end of the year drew nigh, while Caridwen was in the fields gathering herbs, it chanced that the three magic drops flew out of the cauldron, and fell on the finger of Gwion Bach. They scalded his hand so that he promptly put it to his mouth, and sucked his fingers; and immediately he became very wise, and knew all that Caridwen meant to do to him, and his need of guarding against her wily plots! He fled from the house, therefore, and ran towards his own land; and the cauldron, left unstirred, burst in two, and the poisonous liquid ran out of the door, and into a stream where the horses of Gwyddno were drinking; and when they had drunk of the poisoned water they all died.