One of my family friends used to work at a preparation plant for scientific samples, and he had this story to tell:
One of the things they had was pure caffeine. It was a white powder, and was extremely strong and extrememly bitter. One Sunday, as he was going in to work (something about making moth food), he told a friend about it; the next week, several friends showed up and asked him for some. He figured "what the hell, they never use the stuff anyway", and gave each person a couple tablespoons (I think) of the stuff in plastic bags, warning them of the strength of the caffeine.
Later that day, they go to a resturant. Someone dumps about half a bag into a cup of coffee and takes a sip, then complains that he feels a little sick. The family friend says "let me try!" and downs the whole cup. Next day he's in a cold sweat and throws up about eight times; he can't stand the smell or taste of coffee for months afterwards.
There is no sig.