(Chemical Heritage Foundation)

Sir Isaac Newton — the 17th-century scientist, mathematician and father of physics? Yeah, you know him.

But you may not know Newton was super into alchemy, a medieval "science" that preceded chemistry. Practitioners believed it was possible to transform one metal into another. The ultimate goal was figuring out how to transform lead into gold, and the elusive "Philosophers' Stone" was a substance theorized to do just that.

A newly discovered manuscript, written in Newton's hand, underscores his fascination with what's now considered nothing more than mystical pseudoscience. The document, held in a private collection for decades and bought earlier this year by the Chemical Heritage Foundation, describes how to make an essential ingredient of the Philosophers' Stone.

This document is one of many handwritten by the English physicist best known for establishing the law of universal gravitation.

 Sir Isaac Newto. (Library of Congress Prints and Photographs Division) Sir Isaac Newton (Library of Congress Prints and Photographs Division)

"Newton was intensely interested in alchemy almost his whole life," said James Voelkel, curator of rare books at the foundation's Othmer Library of Chemical History. "These alchemical manuscripts consist of about a million words he wrote in his own hands."

Alchemy, also called "chymistry" in England back in the 17th century, preoccupied Newton for decades. Following his death, many of his manuscripts were held by his family until they were auctioned by Sotheby's in 1936. Dozens of private collectors bought his alchemical manuscripts, which had been labeled "not fit to be printed" when Newton died in 1727. Most of these papers have since been donated to Cambridge, except for a handful like the one acquired by the Chemical Heritage Foundation.

It wasn't until after Newton's time that the definition of a chemical element, as we understand it today, was developed. But while Newton was around, many thought that metals were comprised of multiple compounds, including a mercuric or sulfuric principle. Changing one of those principles could change a metal, so goes the logic.

So given that context, alchemy didn't seem so crazy.

"What's a little bit more crazy is the notion that there's this Philosophers' Stone that allows you to do this operation automatically," Voelkel said. "Heat up, molten a bunch of lead, toss the Philosophers' Stone into it, and transmute automatically."

This newly discovered manuscript, entitled "Preparation of [Sophick] Mercury for the [Philosphers'] Stone," is Newton's handwritten copy of a recipe authored by a famed alchemist, Harvard-educated George Starkey. (Starkey circulated his writings under the name of a mysterious alter-ego, Eirenaeus Philalethe). This philosophic, or sophick, mercury was supposed to break a metal down into its various components.

Newton likely copied the recipe from another manuscript before Starkey published it in 1678, underscoring just how connected Newton was in alchemical circles.

On the backside of the manuscript, as was Newton's habit, he jotted down lab notes for another alchemical process.

Alchemists often used coded language and allegories to conceal what they were doing. The thinking was sharing such knowledge so broadly would cheapen it and "only the worthy would understand what you were saying," explained Voelkel. That, and transmutation was illegal in places like England.

But Newton applied the same diligence he used in other fields of inquiry to the study of alchemy; he compiled giant concordances classifying those elusive, coded terms.

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

In other words, he did this "magic" like it was a science – because as far as he was concerned, that's what it was.

The foundation's manuscript will be housed in the library and available for scholars to study, and an electronic copy will be shared with an Indiana University project, the Chymistry of Isaac Newton.

Newton played a huge role in the scientific revolution; he helped establish modern physics.

But one of the things typically left out of the narrative of how modern science was developed during the 16th and 17th centuries is the development of chemistry, Voelkel said. "Unlike with physics, by the end of the 17th century, there isn't a clear victory. Chemistry is still muddling."

"You have Newton, so renowned for cracking the physics part of it, he's muddling along with the rest of the 17th-century people," Voelkel said.  "In some ways, it's so difficult that even Newton couldn't solve it."