At the courts of sixteenth-century Europe, a number of princely physicians and surgeons tested promising poison antidotes on condemned criminals. These tests were contrived trials, in which a convict took a deadly poison followed by the antidote. The medics sometimes shared detailed descriptions of their poison trials in printed publications or private correspondence, much as they shared case histories of ill patients. Yet these very same physicians disputed the value of remarkably similar tests on animals conducted by charlatans and empirics in marketplace shows. Sometimes, however, these worlds overlapped directly. In 1583, an empiric named Andreas Berthold published a work in Latin praising the virtues of a marvellous new drug, a clay called ‘Silesian terra sigillata’. Berthold presented the drug as a perfect Paracelsian remedy for poison and, like most antidotes, useful against many other illnesses as well. While such lofty claims might easily have been disregarded, Berthold noted that his readers did not have to ‘trust me on my bare words’. He concluded his book with three testimonial letters from powerful figures – two German princes and one town mayor – about trials they had conducted on the drug in 1580 and 1581. In all three cases, physicians had given poison to test subjects (two used dogs, one a condemned criminal), followed by the antidote. In every case, the subjects who were given the Silesian terra sigillata survived the poison. These testimonial letters provided official legitimacy to an alchemical empiric, in the form of tests conducted by physicians. Meanwhile, other alchemists began to use a different form of testimony to demonstrate the marvellous effects of their antidote cure-alls: testimonial letters from patients describing their miraculous recoveries, which physicians derided as a perversion of the case history. Some of these alchemists likewise ridiculed the poison trial as a lowly and irrelevant form of proof. This talk examines the overlap between the genres of poison antidote and panacea and the debates these drugs engendered in attempts to ‘prove’ their efficacy.