In monte Cyllenio Tiresias Eueris filius pastor dracones venerantes dicitur baculo percussisse alias calcasse. Ob id in mulieris figuram est conversus. Postea monitus a sortibus in eodem loco dracones cum calcasset redit in pristinam speciem.
--Hyginus, Fabulae 75
It is said that when the shepherd Tiresias saw two snakes mating, he struck one with a stick [others, however, say he kicked them]. Because of this, he was turned into a woman (in mulieris figuram). Later on, obeying a prophecy, he kicked mating snakes in the same place and returned to his original form.