Passage 5.27.3
οὗτός ἐστιν ὁ ἵππος ὅτῳ καὶ τὸ ἱππομανὲς λόγῳ τῷ Ἠλείων ἔγκειται· δῆλα δὲ καὶ ἄλλως ἐστὶν ἀνδρὸς μάγου σοφίᾳ γενέσθαι τὰ συμβαίνοντα τῷ ἵππῳ. μέγεθος μὲν ἢ εἶδος ἵππων ἀποδεῖ πολλῷ, ὅσοι τῆς Ἄλτεως ἐντὸς ἑστήκασι, πρὸς δὲ ἀποκέκοπταί τε τὴν οὐρὰν καὶ ἔστιν ἐπὶ τῷ τοιῷδε ἔτι αἰσχίων· οἱ δὲ ἵπποι οἱ ἄρσενες οὔτι που τοῦ ἦρος μόνον ἀλλὰ καὶ ἀνὰ πᾶσαν ἐπʼ αὐτὸν ὀργῶσιν ἡμέραν.
This is the horse concerning which the legend of the "hippomanes" told by the Eleans is maintained. Clearly in other respects also, what happened to the animal was due to the cunning of a magician. It falls far short in size and appearance of all the horses that stand within the Altis; moreover, its tail has been cut off, making it even more disgraceful in this state. Male horses, throughout the entire day and not merely in springtime, are madly attracted to it.