Plutarch, Symp. 5,2 675 AB
“Setting aside the proposal that Achilles was offering out prizes for speeches at the funeral, I said that when he was burying Pelias, Akastas his son put on a context of poetry and that the Sibyl was victor. When many people gathered around me and were asking where my proof was for so unbelievable and impossible an account, I was lucky enough to remember that Aleskandros provides this account in his On Libya.
I was adding, “This story is not a well-known one either, but I think that it will appeal to many of you to read the writing of Polemon the Athenian called On the Treasures of Delphi….There, you will discover the account written that in the Treasury of the Sikyonians there once was a golden book dedicated by Aristomakhe of Erythiai who was victor twice in epic poetry at the Isthmian games.”
ὡς δὴ καὶ λόγων ἆθλα τοῦ ᾽Αχιλλέως προθέντος ἀφείς, εἶπον ὅτι καὶ Πελίαν θάπτων ῎Ακαστος ὁ υἱὸς ἀγῶνα ποιήματος παράσχοι, καὶ Σίβυλλα νικήσειεν. ἐπιφυομένων δὲ πολλῶν καὶ τὸν βεβαιωτὴν ὡς ἀπίστου <καὶ> παραλόγου τῆς ἱστορίας ἀπαιτούντων, ἐπιτυχῶς ἀναμνησθεὶς ἀπέφαινον ᾽Ακέσανδρον ἐν τῶι Περὶ Λιβύης ταῦθ᾽ ἱστοροῦντα. ῾καὶ τοῦτο μέν᾽ ἔφην ῾τὸ ἀνάγνωσμα τῶν οὐκ ἐν μέσωι ἐστίν, τοῖς δὲ Πολέμωνος τοῦ ᾽Αθηναίου Περὶ τῶν ἐν Δελφοῖς θησαυρῶν (IV) οἴμαι [ὅτι] πολλοῖς ὑμῶν ἐντυγχάνειν ἐπιμελές ἐστι ….· ἐκεῖ νῦν εὑρήσετε γεγραμμένον, ὡς ἐν τῶι Σικυωνίων θησαυρῶι χρυσοῦν ἀνέκειτο βιβλίον, ᾽Αριστομάχης ἀνάθημα τῆς ᾽Ερυθραίας, ἐπικῶι ποιήματι δὶς ῎Ισθμια νενικηκυίας.