Folk medicine practitioners in 16th-century Europe left ingredients and fingerprints smudged on their manuals while developing remedies for minor ailments. Now, researchers are studying the chemical traces Renaissance people left behind to understand how they experimented with novel cures.

Two German medical manuals — "How to Cure and Expel All Afflictions and Illnesses of the Human Body" and "A Useful and Essential Little Book of Medicine for the Common Man" — were published in 1531 by eye doctor Bartholomäus Vogtherr. His systematically gathered recipe books for common ailments, like hair loss and bad breath, quickly became bestsellers in Renaissance domestic medicine.