It may sound like the plot of a Dan Brown novel, but this story certainly isn’t fiction. Researchers have finally decoded a mystical manuscript that has confounded experts for centuries, revealing the bizarre inner workings of an 19th-century Masonic organisation.
Known as the Copial Cipher, the 105-page document was written in Germany over 250 years ago, using complex code that had seemed uncrackable. Researchers used a combination of cutting-edge technology and human intuition to unlock the document’s secrets.
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The document was reportedly an instruction manual for setting up society initiation ceremonies and suggested to scare tactics to frighten the initiates. Suggested initiation procedures range from the uncomfortable (plucking pledges’ eyebrows) to the downright unpleasant (telling candidates they should “prepare to die”).
Another passage outlined how to identify fellow society members in every day life. When one member asks how “Hans” is, the other should respond by mentioning a name that begins with the second letter of the first name — for example, “He’s with Anton.”
Kevin Knight, a computer scientist at the University of Southern California, worked with two colleagues from Sweden to crack the cipher and says the discovery opens up a whole new realm of possibilities. “This opens up a window for people who study the history of ideas and the history of secret societies,” Knight said in a press release. “Historians believe that secret societies have had a role in revolutions, but all that is yet to be worked out, and a big part of the reason is because so many documents are enciphered.”
Buoyed by the breakthrough, Knight and his colleagues are now targeting other unsolved ciphers, including those sent to newspapers by the infamous Zodiac Killer. Knight hopes his complex techniques can uncover the identity of the man who killed at least five people in Northern California during the late ’60s.
Jak Phillips is a contributor at TIME. Find him on Twitter at @JakPhillips. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.