John Rhys, Celtic Folklore
Once on a time, in the fourteenth century, the wife of a man at Corwrion had twins, and she complained one day to a witch, who lived close by, at Tydyn y Barcud, that the children were not getting on, but that they were always crying day and night.
"Are you sure that they are your children?" asked the witch, adding that it did not seem to her that they were like hers.
"I have my doubts also," said the mother.
"I wonder if somebody has exchanged children with you," said the witch.
"I do not know," said the mother. "But why do you not seek to know?" asked the other.
"But how am I to go about it?" said the mother.
The witch replied, "Go and do something rather strange before their eyes and watch what they will say to one another."
"Well, I do not know what I should do," said the mother.
"Well," said the other, "take an eggshell, and proceed to brew beer in it in a chamber aside, and come here to tell me what the children will say about it."
She went home and did as the witch had directed her, when the two children lifted their heads out of the cradle to find what she was doing--to watch and to listen.
Then one observed to the other, "I remember seeing an oak having an acorn," to which the other replied, "And I remember seeing a hen having an egg"; and one of the two added, "But I do not remember before seeing anybody brew beer in the shell of a hen's egg."
The mother then went to the witch and told her what the twins had said one to the other; and she directed her to go to a small wooden bridge not far off, with one of the strange children under each arm, and there to drop them from the bridge into the river beneath.
The mother went back home again and did as she had been directed. When she reached home this time, she found to her astonishment that her own children had been brought back.
Source: John Rhys, Celtic Folklore: Welsh and Manx (Oxford: Oxford University Press, 1901), vol. 1, pp. 62-63.
