16th-century Swiss physician Paracelsus was frustrated with established medical practice and academia and he was sometimes on the lam because of his beliefs. He wrote at length about the idea that items in the natural world carried “signatures” in their appearance that could tell you visually how they could be used medicinally.

Research:

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Paracelsus. “Of the supreme mysteries of nature. : Of the spirits of the planets. of occult philosophy. The magical, sympathetical, and antipathetical cure of wounds and diseases. The mysteries of the twelve signs of the zodiack.” London. 1656. Accessed online: https://archive.org/details/paracelsvsofsupr00para/page/n9/mode/2up
Simon, Matt. “Fantastically Wrong: The Strange History of Using Organ-Shaped Plants to Treat Disease.” Wired. July 16, 2014. https://www.wired.com/2014/07/fantastically-wrong-doctrine-of-signatures/
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Waite, Arthur Edward. “Lives of alchemystical philosophers based on materials collected in 1815 : and supplemented by recent researches with a philosophical demonstration of the true principles of the magnum opus, or great work of alchemical re-construction, and some account of the spiritual chemistry.” London. G. Redway. 1888. Accessed online: https://archive.org/details/livesofalchemyst1888wait

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Paracelsus and the Doctrine of Signatures

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Paracelsus and the Doctrine of Signatures