After 10 minutes' searching through my library, I have found my copy of The Journey Through Wales, and found the passage that induced much WTF-ery:
"In Eastern countries, when the beaver finds that it cannot evade the dogs which are following it by its scent, it saves itself by self-mutilation. By some natural instinct it know which part of its body the hunter really wants. The creature castrates itself before the hunter's eye and throws its testicles down. It is because of this act of self-castration that it is called 'castor' in Latin. [Ed: it really, really isn't] If a beaver which has already lost its testicles is hard pressed a second time by the hounds, it rushes to the top of a hillock, cocks up one of its hind-legs and shows the hunter that the organs which he is really after have already been cut off."
There follows a bunch of Classical quotations to show that he's read Wikipedia. I mean, that he's studied hard.
That's from the Penguin Classic The Journey through Wales and the Description of Wales, Gerald of Wales, translated by Lewis Thorpe (1978)