Archimedes' principle
Cao Cao later regretted executing Hua Tuo when his son Cao Chong (196–208), a child prodigy who may have independently discovered and used Archimedes' principle, died from illness. The "Sanguozhi" does not specify Hua Tuo's exact date of death, but since Cao Chong died in 208, Hua Tuo could not have lived past that year.