Illustration of 'washing-up water' (xiwan shui) from Shiwu bencao (Materia dietetica), a dietetic herbal in four volumes dating from the Ming dynasty (1368-1644) © Wellcome Collection, London 

The identity of the author and artists is unknown. It contains entries on over 300 medicinal substances and is illustrated by almost 500 paintings in colour. The illustration shows a man washing dishes in a kitchen. The text states: Washing-up water can treat malign sores which have failed to heal after a long period. The washing-up water is boiled and salted and used to bathe the lesions. The effects are immediate.