 In 1596, Li Shizhen recommended tea made from qinghao specifically to treat malaria symptoms in his "Compendium of Materia Medica".Researcher Tu Youyou discovered that a low-temperature extraction process could isolate an effective antimalarial substance from the plant.Tu says she was influenced by a traditional Chinese herbal medicine source, "The Handbook of Prescriptions for Emergency Treatments", written in 340 by Ge Hong, which states that this herb should be steeped in cold water.