A Czechoslovakian monk turned physician in 1819, Jan Purkinje held a great deal of skepticism toward the recommended doses of medicines prescribed by physicians in his day. He considered them far too small and "nothing but mysticism" [source: Altman]. So he set out to determine proper dosages by ingesting the drugs himself, while paying close attention to the effects the drugs had on his mental and physical faculties.
Purkinje tried a number of medicinal plants, like foxglove (digitalis), which slows the heart and is known to blur vision. To study the physiology of vision, he overdosed on foxglove and sketched and described the vision problems he endured. He ingested nightshade (atropine), which stops the heart by overexerting it, to study its effects on vision too. We now use atropine to dilate pupils thanks to Purkinje. And when word got out that this trained physician was experimenting on himself, others asked for his help. One of his teachers gave him extracts of ipecac and asked him to describe his reactions. By the end of the three-week experiment, he conditioned a vomiting response to the sight of any brown powder that looked like the drug.
Over the years, Purkinje self-experimented with nutmeg, camphor, turpentine and a host of other drugs, which led to an increased understanding in dosage and drug interactions.