The incredible story of how hatmakers really did ‘go mad’ 300 years ago

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The expression 'mad as a hatter' is based from the real-life behavior of hatters from the 17th century. It turns out that the process they used to make their hats was poisoning them and driving them insane. It wasn't until 1941 that hatters discovered what was causing them to behave so strangely. Read more: http://www.businessinsider.com/sai FACEBOOK: https://www.facebook.com/techinsider TWITTER: https://twitter.com/techinsider INSTAGRAM: https://www.instagram.com/businessinsider/ TUMBLR: http://businessinsider.tumblr.com/