The Mad Hatter's Tale

The character of the Mad Hatter has been popularized by Lewis Carroll's Through the Looking Glass, but people were familiar with the Mad Hatter idea before Lewis ever put pen to paper. The phrase "mad as a hatter" likely had origins in the mercury that hatters used to use for softening whalebone for hat brims. Over time, exposure to the mercury would cause brain damage, slurred speech, and distorted eyesight. Advanced mercury poisoning causes psychotic symptoms and hallucinations. Since the process was so gradual, it was a while before people realized why their local hatters were going mad.