The medieval sleep sponge
Before an operation, medieval surgeons used a “sleep sponge”: a sponge was soaked in the juice of opium poppy, mandrake and henbane and dried, then moistened with hot water and laid over the patient’s mouth and nose. In 1363 the surgeon Guy de Chauliac warned that the method could cause lasting harm and death. To wake the patient there was a “wake-up sponge” soaked in fennel juice or vinegar.
Source: Jürgen Leo Müller, “Love potions and the ointment of witches: historical aspects of the nightshade alkaloids”, Journal of Toxicology: Clinical Toxicology 36(6), 1998 (Müller, Clin Toxicol, 1998). This is a folk record, not a treatment recommendation.
Flour sprinkled on wounds: yarrow