Artemisinin is an anti-malarial drug found in Artemisia annua, which was used in traditional Chinese medicine. However, it was one of many malarial treatments in traditional Chinese medicine and the rest were likely totally useless.
Ignaz Semmelweis proved the efficacy of antiseptic procedures to reduce deaths from ‘childbirth fever’ - years before Louis Pasteur formulated the germ theory of disease that became generally accepted.
However…
I was reading about asclepeions (temple/hospitals of Asclepius) in ancient Greece. Part of the treatment they provided was a ritual bath followed by sleep where the god would (hopefully) visit the patient in a dream. One article I read suggested that the prescription of rest plus basic hygeine was probably better than nothing.