Passage 10.6.4
οἱ δὲ Καστάλιόν τε ἄνδρα αὐτόχθονα καὶ θυγατέρα ἐθέλουσιν αὐτῷ γενέσθαι Θυίαν, καὶ ἱερᾶσθαί τε τὴν Θυίαν Διονύσῳ πρῶτον καὶ ὄργια ἀγαγεῖν τῷ θεῷ· ἀπὸ ταύτης δὲ καὶ ὕστερον ὅσαι τῷ Διονύσῳ μαίνονται Θυιάδας καλεῖσθαι σφᾶς ὑπὸ ἀνθρώπων· Ἀπόλλωνος δʼ οὖν παῖδα καὶ Θυίας νομίζουσιν εἶναι Δελφόν. οἱ δὲ μητρὸς μὲν Μελαίνης φασὶν αὐτόν, θυγατρὸς Κηφισοῦ.
They say Castalius was an autochthonous man and had a daughter named Thyia; she was the first to sacrifice to Dionysus and to celebrate orgiastic rites to the god. Because of her, all the women who afterwards became frenzied for Dionysus have been called Thyades by people. Indeed, they hold Delphi to be the son of Apollo and Thyia. Others, however, say he was born from a mother named Melaina, daughter of Cephisus.