How Scholars Cracked a Medieval Alchemist’s Secret Code

November 16, 2021

Written in a puzzling Latin cipher, it contains his formula for eternal life.

In summer 2018, Megan Piorko was deep into research for her doctoral dissertation on 16th- and 17th-century alchemist and physician Arthur Dee.

On a beautiful London day, she called up a little-studied alchemical notebook from the archives of the British Library, Sloane MS 1902. Immediately, Piorko was intrigued. The notebook, to which both Dee and his famous alchemist, polymath father, John Dee, had contributed, was “odd,” she says.

The fabric and leather-bound manuscript has 31 leaves of both parchment and paper. Certain pages are written upside down, so Piorko had to flip the entire notebook to read it. It was on one of those inverted pages that she found a puzzling passage written in code.

On an opposing page was a strange-looking table filled with letters. She didn’t know it at the time, but the coded text had been hiding the alchemists’ recipe to the elixir of life—what those in the profession called the “Philosopher’s Stone.”

Fast forward a year and change to November 28, 2019, and Amsterdam’s 10th Annual Society for the History of Alchemy and Chemistry Post-Graduate Workshop. Piorko, who was finishing her PhD at Georgia State University, had organized the event, in a hall donated by none other than The Da Vinci Code author Dan Brown.

At a post-conference happy hour in a cozy pub, Piorko and a friend, digital humanities scholar Sarah Lang from the University of Graz, found themselves discussing the peculiar notebook. “I was like, ‘Oh, it actually has this really cool cipher in it,’ and so we were just looking at it on my phone,” says Piorko.

They inspected Piorko’s images of the 177-word encrypted text, which carried the title, “Hermeticae Philosophiae medulla” or “Marrow of the Hermetic Philosophy.” After the Latin title, everything else looks like gibberish: words such as “ozxkwxfg” and “qqdz” are spaced out across several pages. On the accompanying table, a two-letter heading is followed by two rows of 11 letters each.

“[Lang] tried to initially crack it on a napkin,” Piorko laughs. Though she wasn’t able to solve it, Lang did learn that the text was encrypted using a substitution cipher, where letters from the original text are swapped out for different ones. She made this conclusion based on the table, which would have required a keyword to be applied to the text.

“I think it would actually be possible” to crack the cipher on a napkin, says Lang, “if it had been a cipher on the cipher level of the time, but it turned out to be a very well-encrypted cipher.” Medieval ciphers “were mostly really bad,” says Lang. But this one wasn’t like most.

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