The author of the Aegimius says in the second book that Thetis used to throw the children she had by Peleus into a cauldron of water, because she wished to learn whether they were mortal . And that after many had perished Peleus was annoyed, and prevented her from throwing Achilles into the cauldron.
Hesiod and Acusilaus say that she (Io) was the daughter of Peiren. While she was holding the office of priestess of Hera, Zeus seduced her, and being discovered by Hera, touched the girl and changed her into a white cow, while he swore that he had no intercourse with her. And so Hesiod says that oaths touching the matter of love do not draw down anger from the gods:
And (Hera) set a watcher upon her (Io), great and strong Argus, who with four eyes looks every way. And the goddess stirred in him unwearying strength: sleep never fell upon his eyes; but he kept sure watch always.
Hesiod (says there were so called) because they settled in three groups: And they all were called the Three-fold people, because they divided in three the land far from their country. For (he says) that three Hellenic tribes settled in Crete, the Pelasgi, Achaeans and Dorians. And these have been called Three-fold People.