The Metamorphoses of Ovid, Books I-VII

If it is the fact, as many antiquarians suppose, that much of the Grecian mythology was derived from that of the Egyptians, there can be but little doubt that their system of the Elysian Fields and the Infernal Regions was derived from the Egyptian notions on the future state of man. The story too, of Cerberus is, perhaps, based upon the custom of the Egyptians, who kept dogs to guard the fields or caverns in which they kept their mummies.

It is, however, very possible that the story of Cerberus may have been founded upon a fact, or what was believed to be such. There was a serpent which haunted the cavern of Tænarus, in Laconia, and ravaged the districts adjacent to that promontory. This cave, being generally considered to be one of the avenues to the kingdom of Pluto, the poets thence derived the notion that this serpent was the guardian of its portals. Pausanias observes, that Homer was the first who said that Cerberus was a dog; though, in reality, he was a serpent, whose name in the Greek language signified ‘one that devours flesh.’ The story that Cerberus, with his foam, poisoned the herbs that grew in Thessaly, and that the aconite and other poisonous plants were ever after common there, is probably based on the simple fact, that those herbs were found in great quantities in that region.

Women, using these herbs in their pretended enchantments, gave ground for the stories of the witches of Thessaly, and of their ability to bring the VII. 469-481 moon down to the earth by their spells and incantations; which latter notion was probably based on the circumstance, that these women used to invoke the Night and the Moon as witnesses of their magical operations.