Passage 5.21.3
πρῶτοι δὲ ἀριθμὸν ἓξ ἐπὶ τῆς ὀγδόης ἔστησαν καὶ ἐνενηκοστῆς Ὀλυμπιάδος· Εὔπωλος γὰρ Θεσσαλὸς χρήμασι διέφθειρε τοὺς ἐλθόντας τῶν πυκτῶν, Ἀγήτορα Ἀρκάδα καὶ Πρύτανιν Κυζικηνόν, σὺν δὲ αὐτοῖς καὶ Φορμίωνα Ἁλικαρνασσέα μὲν γένος, Ὀλυμπιάδι δὲ τῇ πρὸ ταύτης κρατήσαντα. τοῦτο ἐξ ἀθλητῶν ἀδίκημα ἐς τὸν ἀγῶνα πρῶτον γενέσθαι λέγουσι, καὶ πρῶτοι χρήμασιν ἐζημιώθησαν ὑπὸ Ἠλείων Εὔπωλος καὶ οἱ δεξάμενοι δῶρα παρὰ Εὐπώλου. δύο μὲν δὴ ἐξ αὐτῶν ἔργα Κλέωνος Σικυωνίου· τὰ δὲ ἐφεξῆς τέσσαρα ὅστις ἐποίησεν, οὐκ ἴσμεν.
They were the first to set up statues, six in number, in the ninety-eighth Olympiad. For Eupolus, a Thessalian, had bribed with money the boxers who had come forward—Agetor of Arcadia and Prytanis from Cyzicus, and along with them Phormion, who was from Halicarnassus by birth, and who had previously been victorious at the last Olympiad. This, they say, was the first known offense committed by athletes against the fairness of the competition, and Eupolus, as well as those who accepted gifts from him, were the first whom the Eleans penalized with monetary fines. Two of these statues were the work of Cleon of Sicyon; but who made the other four statues that followed him, we do not know.