Oh, and another one: Porphyry says [in his Life of Pythagoras XLI] that the Pythagoreans called the seven planets, "the hounds of Persephone." He doesn't say why, but it makes sense if we equate the material world with Hades: Persephone is the mistress of the material cosmos, the planets are the guardians that keep us here, and they are forever nipping at us...