Isaac Newton is often considered one of the founding fathers of modern science. Not only did he help develop the theory of gravity, but he invented calculus and discovered the three laws of motion that physics students still learn today. But while Newton was one of the most influential scientists of the 17th century, he was also a practicing alchemist who longed to find a method for turning lead into gold. Now, historians have rediscovered a manuscript handwritten by Newton that details a recipe for making one of the critical elements thought necessary to create the Holy Grail of alchemy: the Philosopher’s Stone.

Alchemy’s roots lie deep in medieval mysticism. While it is now considered pseudoscience, it was a kind of precursor to modern chemistry as practitioners believed it could magically transform materials with the right recipes. During the 17th century, alchemy was considered a perfectly reasonable field of study and Newton was just as interested in it as he was in physics and mathematics, Sarah Laskow reports for Atlas Obscura.

“Alchemists were the first to realize that compounds could be broken down into their constituent parts and then recombined. Newton then applied that to white light, which he deconstructed into constituent colors and then recombined,” science historian William Newman tells Michael Greshko for National Geographic. “That’s something Newton got from alchemy.”

The newly uncovered document was kept in a private collection for many years, but was recently acquired by the Chemical Heritage Foundation. Titled “Preparation of Mercury for the Stone,” the manuscript appears to be a handwritten copy of a recipe to make a key ingredient of the Philosopher’s Stone originally created by alchemist George Starkey, Elahe Izadi reports for the Washington Post. This “philosophic mercury,” as it was known, could supposedly break down metals into their basic components before the Stone transmuted them into gold. The back of the manuscript also contains notes written by Newton that detail other alchemical processes.

“[They] may well be laboratory notes of a process Newton had tried or was thinking of trying,” James Voelkel, a rare books curator at the foundation’s Othmer Library of Chemical History, tells James Rogers for Fox News. “Like many of us, when Newton needed a place to jot something down, he would sometimes just turn over a manuscript and write on the blank page on the back.”

For centuries, scientists and historians tried to downplay Newton’s alchemical interests, as the field was discredited shortly after his death in 1727. But in recent years, science historians have begun examining these documents for their insights into Newton’s analytical mind. Unlike most other alchemists, who tried to hide their methods from the unlearned and “unworthy,” Newton diligently documented his lab techniques, Izadi reports.

"Newton is an interesting alchemist because he's systematic about it," Voelkel tells Izadi. "He would reference back to each individual alchemical author, which page they'd use this term, and tried to do a data-driven analysis."