Passage 1.18.1
τὸ δὲ ἱερὸν τῶν Διοσκούρων ἐστὶν ἀρχαῖον, αὐτοί τε ἑστῶτες καὶ οἱ παῖδες καθήμενοί σφισιν ἐφʼ ἵππων. ἐνταῦθα Πολύγνωτος μὲν ἔχοντα ἐς αὐτοὺς ἔγραψε γάμον τῶν θυγατέρων τῶν Λευκίππου, Μίκων δὲ τοὺς μετὰ Ἰάσονος ἐς Κόλχους πλεύσαντας· καί οἱ τῆς γραφῆς ἡ σπουδὴ μάλιστα ἐς Ἄκαστον καὶ τοὺς ἵππους ἔχει τοὺς Ἀκάστου.
The sanctuary of the Dioscuri is ancient; the Dioscuri themselves are standing, and their sons are seated upon horses. Here Polygnotus painted the marriage of the daughters of Leucippus, including the Dioscuri's role in it, while Micon depicted the expedition of Jason and his companions sailing to Colchis. The painting particularly emphasizes Acastus and the horses of Acastus.