Chloroform
Sir James Young Simpson, Baronet of Strathavon and the City of Edinburgh, was a Scottish obstetrician who discovered chloroform and administered it as an anaesthetic to women in labour.
Simpson and two of his doctor friends realised chloroform’s properties during an 1847 experiment in his dining room, when they found it first raised their moods, and then knocked them out until morning.
The organic compound, also known as trichloromethane and CHCI3, was popularised when Queen Victoria used it during the birth of her children. It was abandoned decades later due to its dangerous toxicity.
Despite popular myth, it is almost impossible to knock someone out using a chloroform-soaked handkerchief, as the victim would need to inhale for at least five minutes. However chloroform has been implicated in crimes in combination with other drugs.