Swedish King Gustav III disliked coffee. He believed it was unhealthy. To prove this, he hired identical twins and made one drink coffee every day and the other tea for the rest of their lives. The twins outlived both the doctors and the king himself.
He believed that it made people behave in a bad manner.
Some other versions of the story state that he made use of two prisoners who were sentenced to death. If they were to participate in his experiment, he would offer them life imprisonment instead.
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