Hesiod, the Homeric Hymns and Homerica/Hymn XVII (To the Dioscuri)
TO THE DIOSCURI
Sing, clear-voiced Muse, of Castor and Polydeuces, the Tyndaridae, who sprang from Olympian Zeus. Beneath the heights of Taÿgetus stately Leda bare them, when the dark-clouded Son of Cronos had privily bent her to his will.
Hail, children of Tyndareus, riders upon swift horses!