Ergot appears twice in arguments that are cited far more confidently than the evidence supports.
The first is Eleusis. For nearly two thousand years the Mysteries at Eleusis initiated Greeks in a rite whose central experience was never disclosed, and initiates drank a barley preparation called the kykeon. In 1978 Wasson, Hofmann and Ruck proposed that the kykeon was psychoactive and that the agent was ergot growing on the barley, water-extracted to separate the soluble alkaloids from the toxic ones. The attraction of the theory is that it explains why an experience so consistently described as overwhelming could be produced on schedule for thousands of people. The objections are serious: no ancient source describes anything of the kind, the required separation is delicate, and the argument runs backwards from the effect to a cause that would explain it. It is a hypothesis and the atlas records it as one.
The second is Salem. Linnda Caporael proposed in 1976, and Mary Matossian developed at length, that the 1692 accusations followed convulsive ergotism in the local rye. Historians of Salem have largely rejected it. The symptom pattern does not fit well, the afflicted were concentrated in ways an infected food supply would not produce, and the documentary record supports explanations grounded in the community's own conflicts.
Both claims share a shape worth noticing: a physical cause offered for a religious phenomenon, appealing precisely because it is tidy.