How to Prevent Pregnancy, c. 1260

British Library Sloane MS 75, f. 87r

"A weasel placed on a scorpion bite helps greatly... if its heel is taken from it while it still lives and is placed on a woman, she will not get pregnant as long as it is there." 

Albertus Magnus, De animalibus

As if you needed another reason to keep a live weasel in your bedroom.