Passage 3.26.2
Θαλαμῶν δὲ ἀπέχει σταδίους εἴκοσιν ὀνομαζομένη Πέφνος ἐπὶ θαλάσσῃ. πρόκειται δὲ νησὶς πέτρας τῶν μεγάλων οὐ μείζων, Πέφνος καὶ ταύτῃ τὸ ὄνομα· τεχθῆναι δὲ ἐνταῦθα τοὺς Διοσκούρους φασὶν οἱ Θαλαμᾶται. τοῦτο μὲν δὴ καὶ Ἀλκμᾶνα ἐν ᾄσματι οἶδα εἰπόντα· τραφῆναι δὲ οὐκέτι ἐν τῇ Πέφνῳ φασὶν αὐτούς, ἀλλὰ Ἑρμῆν τὸν ἐς Πελλάναν κομίσαντα εἶναι.
About twenty stades distant from Thalamae is a place by the sea named Pephnos. Directly offshore lies a small island no larger than a great rock, which is likewise called Pephnos. The inhabitants of Thalamae say that the Dioscuri were born there. Indeed, I know that Alcman also says this in one of his poems. They add, however, that the twins were no longer reared at Pephnos, but rather that Hermes took them and carried them to Pellana.