Passage 9.38.8
ἔχει δὲ οὐδὲ εἰκότα λόγον τοὺς Ὀρχομενίους μὴ καὶ τὸ χάσμα ἐξευρεῖν καὶ τοῦ Ἡρακλέους ἀναρρήξαντας τὸ ἔργον ἀποδοῦναι τὴν διέξοδον τῷ Κηφισῷ τὴν ἀρχαίαν, ἐπεὶ μηδὲ ἄχρι τῶν Τρωικῶν χρήμασιν ἀδυνάτως εἶχον. μαρτυρεῖ δέ μοι καὶ Ὄμηρος ἐν Ἀχιλλέως ἀποκρίσει πρὸς τοὺς παρὰ Ἀγαμέμνονος πρέσβεις· οὐδʼ ὅσʼ ἐς Ὀρχομενὸν ποτινίσσεται, Hom. Il. 9.381 δῆλα δήπουθεν ὡς καὶ τότε προσιόντων τοῖς Ὀρχομενίοις χρημάτων πολλῶν.
Nor does it make sense that the Orchomenians would not have discovered the chasm and, completing the unfinished work of Heracles, restored the ancient channel for the Cephisus, given that even up to the Trojan War they were not lacking financial means. Homer himself testifies to this point in Achilles' reply to the envoys sent by Agamemnon: "nor all the wealth that flows into Orchomenus"—clearly indicating that even at that time the Orchomenians were in possession of great wealth.