The bezoar, from the Persian word for antidote, is a hardened mass of undigested hair and food from an animal’s gut, yet for centuries it was prized as a stone that could neutralize any poison. This episode traces it from the 12th century physician Ibn Zuhr, credited with first documenting bezoars as antidotes, to the Mongol Empire, where the stones were used in shamanic rituals to summon storms. When trade routes opened in the 16th and 17th centuries, the most prized bezoars came from goats and monkeys in the East Indies, Rudolf II displayed them in his cabinets of curiosity, and a stone was set in a ring linked to Queen Elizabeth I.

In 1567 the surgeon Ambroise Paré offered a cook condemned for stealing silver a deal: take poison, then a bezoar, and walk free if he lived. He died seven hours later. A 1603 English case, Chandelor v. Lopus, ruled for the goldsmith who sold a useless bezoar for 100 pounds, a landmark in caveat emptor. Modern medicine still meets bezoars in the gut, and researchers at the Scripps Institution of Oceanography later found that genuine stones do pull arsenic out of solution.

• Traders tested stones by poisoning a dog with a needle and seeing whether the bezoar saved it
• The modern types: phytobezoars, trichobezoars and Rapunzel syndrome, pharmacobezoars, and lactobezoars in premature infants
• How tannins in unripe persimmons can polymerize into a rock hard diospyrobezoar in the stomach
• A 2013 review of 46 patients treated with Coca-Cola, with complete resolution in 91.3 percent and surgery for only four
• Why Paré’s cook might have lived: brushite and hair keratin trap the two toxic forms of arsenic