royal treatment of being fed a solution of powdered lead and mercury

I looked this up and

In Chinese alchemy, elixir poisoning refers to the toxic effects from elixirs of immortality that contained metals and minerals such as mercury and arsenic. The official Twenty-Four Histories record numerous Chinese emperors, nobles, and officials who died from taking elixirs to prolong their lifespans. The first emperor to die from elixir poisoning was likely Qin Shi Huang (d. 210 BCE) and the last was the Yongzheng Emperor (d. 1735 CE). Despite common knowledge that immortality potions could be deadly, fangshi and Daoist alchemists continued the elixir-making practice for two millennia.

Based alchemists disguising killing the parasiting ruling class as feeding into their fear of death.