The first known medical description of Qinghao lies in a 2000-year-old document called "52 Prescriptions" (168 BCE) that had been unearthed from a Mawangdui Han Dynasty tomb. It details the herb's use for soothing hemorrhoids. Later texts also mention the plant's curative powers. Tu discovered a passage in the Handbook of Prescriptions for Emergencies (340 CE) by Ge Hong that referenced Qinghao's malaria-healing capacity. It said "Take a handful of Qinghao, soak in two liters of water, strain the liquid, and drink." She realized that the standard procedure of boiling and high-temperature extraction could destroy the active ingredient.