Herodotus, Histories 1.61:
“Peisistratus, having seized hold of the tyranny in the aforesaid manner, married the daughter of Megacles in accordance with a previous agreement. Since, however, he already had two children, and it was said that the Alcmeonids were cursed, Peisistratus did not wish to have children with his new wife. And so, he had sex with her in something other than the accustomed manner.”
ἀπολαβὼν δὲ τὴν τυραννίδα τρόπῳ τῷ εἰρημένῳ ὁ Πεισίστρατος κατὰ τὴν ὁμολογίην τὴν πρὸς Μεγακλέα γενομένην γαμέει τοῦ Μεγακλέος τὴν θυγατέρα. οἷα δὲ παίδων τέ οἱ ὑπαρχόντων νεηνιέων καὶ λεγομένων ἐναγέων εἶναι τῶν Ἀλκμεωνιδέων, οὐ βουλόμενός οἱ γενέσθαι ἐκ τῆς νεογάμου γυναικὸς τέκνα ἐμίσγετό οἱ οὐ κατὰ νόμον.