In July 1697, Jacques Sennacques from Lille, France, scribbled a note to his merchant cousin, Pierre le Pers, in The Hague. The topic of discussion was a death certificate of their relative, a topic the nieces and nephews had discussed before, but Le Pers had failed to proceed. The letter was the Renaissance equivalent of a “according to my previous email,” and it was only read for the first time since it was sealed 324 years ago.
But although it has been read, the letter remains unopened. It’s a letter lock, a term coined by MIT curator Jana Dambrogio for letters that use specific folds and slits to seal themselves, without the need for an envelope. Letter lock was the typical way to seal messages in the days before mass-produced envelopes; Queen Elizabeth I of England had at least five different letter lock variants to privatize her correspondence.
In a unique application of the technology, Dambrogio’s team virtually ‘unfolded’ Sennacques’s letter using X-ray microtomography, allowing the researchers to bypass the often damaging process of manually opening a letter. The team’s investigation was published on Tuesday in the journal Nature Communications.
“I remember a feeling of elation, as in, [oh my god] it finally worked out, ”says co-author Rebekah Ahrendt, musicologist at Utrecht University, in an email. “After working with this collection for several years, the effect of ‘I’m probably the first person to read this since it was written’ has worn off a bit … That said, this letter is such a wonderful example of the concerns of normal people right now. “
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It is not known why Le Pers never received the letter – he may have moved given his profession. But the sealed letter remained in the hands of the chief postmasters in The Hague, Simone de Brienne, and his wife, Marie Germain. The couple did not throw away the attached family issue because, at the time, letters were bought by recipients, not paid for by their senders. Some postmasters kept unclaimed letters in case someone eventually came over to buy them. The couple in charge of the mail in The Hague were either hoarders or resolutely optimistic, as they held on to the letters until they died. Thousands of letters in the care of Brienne and Germain were kept in an old suitcase, 600 of which are unopened letters with a lock; it’s an amazing collection of European conversations suspended in time, now called the Brienne Collection. The collection is located in the Sound and Vision museum in The Hague.
Shooting X-rays through the letter written by Sennacques revealed the iron-rich ink that he drew over each fold of the letter. The intensity of the X-rays was about one-third that of the same machine for its original purpose: imaging teeth and bones.
“We’re starting with a very high-resolution CT scan of the folded letter package, which is basically a 3-D X-ray,” said study co-lead author Amanda Ghassaei, the algorithm engineer who led the project and who has previously worked simulating the fold in origami, in an email. “From there, our algorithm detects individual layers of paper in the scan and reconstructs the folded geometry. This computational pipeline allows us to observe writing, watermarks, stamps, internal folds and any other information hidden in the letter package without damaging the original artifact. “
But that was not enough. The team also had to decrypt the folded letter to understand which characters fell where in the unfolded version. To do this, they used a computational flattening script, to deconstruct the letter without touching it. Although an imperceptible jumble of outside characters, wrapped in the khaki paper, the research team was able to extract the message without difficulty.
The research team did not describe the folded layout of Sennacques’ letter in code; the algorithm did the heavy geometric lift.
“The message and intricate internal mechanics of these letters are only known to us because they have been virtually reconstructed,” said study co-author Holly Jackson, a student at MIT and an algorithm engineer on the project. “Our methods are fully automatic, unbiased to scan orientation and require no prior knowledge of the folded geometry of a letter package.”
So to write the new article, the team used X-rays to detect the layout of ink on a piece of ancient paper, they built and implemented an algorithm to virtually unfold that paper, and they described the contents of that letter right next to it. a complex dictionary for the various letter-locking techniques as a larger practice in days before envelopes. In essence, the work was threefold.
The sum of these efforts is a clear plan of action for the approximately 600 letter-locked items that remain in the chest. Cousins’ problems, marital disputes, state secrets – who knows?
It’s as close as history holds its breath.