The apparent incorruptibility of an elixir-takers corpse is Needham and Lus second explanation for the persistent belief in immortality elixirs. They suggest that in some cases a body did not decompose because the deceased had died from mercury or arsenic poisoning, which is forensically known to often preserve a corpse from decay. For a believer in Daoist immortality drugs, even when an elixir-taker had unmistakably died, if the corpse was comparatively undecomposed, that could be interpreted as proof that the adept had become a xian immortal, as well as evidence for the alchemical elixir's efficacy.
Terminal incorruptibility was an ancient Chinese belief associated with jade, gold, and cinnabar. The Baopuzi says, "When gold and jade are inserted into the nine orifices, corpses do not decay. When salt and brine are absorbed into flesh and marrow, dried meats do not spoil. So when men ingest substances which are able to benefit their bodies and lengthen their days, why should it be strange that (some of these) should confer life perpetual?" The abolition of decay was believed to demonstrate the power of elixirs, "the corruptible had put on incorruptibility". Chinese jade burial suits are a better known example of using a mineral to preserve corpses.
There is a possibility that Sun Simiao (above) died from taking mercury elixirs. According to Suns hagiography in the 10th-century Xuxian zhuan' 續仙傳 (Further Biographies of the Immortals), after his death in 682 there was no visible sign of putrefaction, "After more than a month had passed there was no change in his appearance, and when the corpse was raised to be placed in the coffin it was as light as (a bundle of) empty clothes".
The incorruptibility stories about elixir users were not all myth, and recent archeological evidence showed that the ancient Chinese knew how "to achieve an almost perpetual conservation". The 1972 excavation of a tomb at Mawangdui discovered the extremely well-preserved body of Xin Zhui or Lady Dai, which resembled that of "a person who had died only a week or two before". A subsequent autopsy on her corpse found "abnormally high levels" of mercury and lead in her internal organs.