Gǔdài huángdì dōu xiǎng zhǎodào chángshēngbùlǎo de xiāndān.
Ancient emperors all wanted to find the elixir of immortality.
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history
Taoist alchemists (炼丹术士) spent centuries brewing 仙丹 from mercury, cinnabar, and herbs. Several Tang emperors died of mercury poisoning from these "immortality pills".