Passage 10.24.7
ἰοῦσι δὲ ὡς ἐπὶ τὸν ναὸν αὖθις μετὰ τοῦ λίθου τὴν θέαν ἐστὶν ἡ Κασσοτὶς καλουμένη πηγή· τεῖχος δὲ οὐ μέγα ἐπʼ αὐτῇ καὶ ἡ ἄνοδος διὰ τοῦ τείχους ἐστὶν ἐπὶ τὴν πηγήν. ταύτης τῆς Κασσοτίδος δύεσθαί τε κατὰ τῆς γῆς λέγουσι τὸ ὕδωρ καὶ ἐν τῷ ἀδύτῳ τοῦ θεοῦ τὰς γυναῖκας μαντικὰς ποιεῖν· τὴν δὲ τῇ κρήνῃ δεδωκυῖαν τὸ ὄνομα τῶν περὶ τὸν Παρνασσὸν νυμφῶν φασιν εἶναι.
As you go again to the temple with the stone, there is on the way a spring called Cassotis which is worth seeing. A small wall stands upon it, and one ascends through this wall to reach the spring. They say that the water from Cassotis sinks underground and, inside the sanctuary of the god, causes the women to prophesy. They say that Cassotis, who gave the spring its name, is one of the nymphs around Parnassus.