Hesiodus autem enarravit, conspicatum aliquando Tiresiam non procul a Cyllene coeuntes angues baculo cecidisse, eumque de viro in mulierem mutatum fuisse, et rursus ita coeuntes eosdem serpentes observasse, et in priorem viri formam rediisse.
--Apollodorus, Bibliothekes III.vi.7, translated into Latin by Thomas Gale (1675)
According to Hesiod, Tiresias caught sight of two mating snakes near Mt. Cyllene, and when he struck them with his walking stick, he transformed from a man to a woman. When he observed those same two snakes mating again a little later, he returned to his original manly form.