Passage 6.20.19
ἔστι δὲ καὶ ἐν Ἰσθμῷ Ταράξιππος Γλαῦκος ὁ Σισύφου· γενέσθαι δὲ αὐτῷ τὴν τελευτὴν λέγουσιν ὑπὸ τῶν ἵππων, ὅτε Ἄκαστος τὰ ἆθλα ἔθηκεν ἐπὶ τῷ πατρί. ἐν Νεμέᾳ δὲ τῇ Ἀργείων ἥρως μὲν ἦν οὐδεὶς ὅστις ἔβλαπτε τοὺς ἵππους· πέτρας δὲ ὑπὲρ τῶν ἵππων τὴν καμπὴν ἀνεστηκυίας χρόαν πυρρᾶς, ἡ ἀπʼ αὐτῆς αὐγὴ κατὰ ταὐτὰ καὶ εἰ πῦρ ἐνεποίει φόβον τοῖς ἵπποις. ἀλλὰ γὰρ ὁ ἐν Ὀλυμπίᾳ Ταράξιππος πολὺ δή τι ὑπερηρκώς ἐστιν ἐς ἵππων φόβον. ἐπὶ δὲ νύσσης μιᾶς Ἱπποδαμείας ἐστὶν εἰκὼν χαλκῆ, ταινίαν τε ἔχουσα καὶ ἀναδεῖν τὸν Πέλοπα μέλλουσα ἐπὶ τῇ νίκῃ.
There is also on the Isthmus a Taraxippos named Glaukos, the son of Sisyphos; they say that he met his end from his horses when Akastos established funeral games in honor of his father. At Nemea in Argive territory there was no hero who harmed horses, but there were rocks standing above the turning point of the racecourse colored with a reddish hue, whose gleam, exactly as if it were fire, inspired fear in the horses. But in fact the Taraxippos at Olympia greatly surpasses all others in terrifying horses. On one of the turning-posts is a bronze image of Hippodameia, holding a ribbon, ready to bind Pelops with it in honor of his victory.