Simone de Beauvoir’s “The Second Sex”. It has the sentence that started the trans movement.

“One is not born, but is rather made, a woman.”

She certainly didn’t intend it this way, but it is wonderful waving this in the faces of TERFs when they tell you a woman is an adult human female. And the beautiful part is that they can’t refute the statement without kicking the legs out from under their entire feminist movement. The Second Sex was huge for feminism.