Paracelsus was responsible for the creation of laudanum, an alcoholic herbal opium preparation. It was in common use up to the 19th century. Like most of the alchemists, he was a notable botanist. He wrote various books, but especially his major work (title translated as: "On the miners' sickness and other diseases of miners"). This listed the occupational hazards of metalworking, including treatment and prevention strategies. He also wrote a book on the human body which contradicted Galen's ideas. He disagreed with Galen's idea of four humours, and instead believed that disease could come from an external source.