Theseus

This dark saying Pittheus apparently understood, and persuaded him, or beguiled him, to have intercourse with his daughter Aethra. Aegeus did so, and then learning that it was the daughter of Pittheus with whom he had consorted, and suspecting that she was with child by him, he left a sword and a pair of sandals hidden under a great rock, which had a hollow in it just large enough to receive these objects.