‘Virtual Unfolding’ Used to Read Unopened Renaissance Letters

When a French lawyer sent a letter to his cousin in the Netherlands 300 years ago, he folded the letter to deter anyone from reading it. That didn’t stop a group of researchers in the year 2021.

The Brienne trunk is a 17th-century trunk of letters bequeathed to the Dutch postal museum in The Hague. The chest contains an extraordinary archive: 2,600 “locked” letters sent from all over Europe to this axis of communication, none of which were ever delivered. Sealed letters from this trunk were scanned by X-ray microtomography and “virtually unfolded” to reveal their contents for the first time in centuries. (Unlocking History Research Group)

(CN) — Long before there were email passwords, there was only the piece of paper and a series of complex folds that could deter tampering.

Jacques Sennacques, a lawyer by trade in Lille, France, wrote a letter to his cousin Pierre Le Pers in the Netherlands to verify the death of a relative. The intricately folded letter dated July 1697 arrived at the postmasters’ house in The Hague.

For whatever reason, the letter was never delivered. It remains closed to this day with the same intricate folds Sennacques made 300 years ago.

But every word has now been read thanks to researchers who found a way to virtually unfold and read the letter. They presented their findings in a study published in the journal Nature Communications on Tuesday.

“Combining exciting new research methods in conservation, computational mathematics, X-ray scanning and the humanities, we go right into the heart of unopened historical letters, accessing their contents for the first time in 300 years, and showing that they are even more revealing when left unopened,” study author Jana Dambrogio with Massachusetts Institute of Technology (MIT) Libraries said in an email.

Computer-generated unfolding sequence of sealed letter DB-1538. Scientists used “virtual unfolding” to read the contents of sealed letter packets from 17th-century Europe without physically opening them. (Unlocking History Research Group)

The letter was likely needed to settle an inheritance dispute over the death of Daniel Le Pers, one of Sennacques’ relatives, the study authors believe.

“Death certificates per se did not exist at this time; instead, a notary would have to write out a copy of the death register of either the town or a church. The notary would then authorize the document with his signature and seal,” said Dambrogio.

To avoid tampering, Sennacques would have deployed a series of folds known as “letterlocking.” The practice predates the envelope and while not foolproof, it’s the next best thing to ensure a letter is read by the intended recipient only.

Picture a wax seal on a sealed envelope. The crest pressed into the hot wax is meant to denote that the letter has been unopened before its arrival. If the seal is broken, then the information in the letter is likely now everyone’s business. And before the age of text messages, school children passed notes to one another folded with their own set of complex folds.

With “letterlocking,” securing a note could become exponentially more complicated based on the amount of time the author put into folding their letter. There is something tangible and at the same ethereal about the system. Because to study “letterlocking” and the locked letters, researchers often need to break them open — and sometimes damage the contents inside.

As luck would have it, the letter Sennacques sent wound up in a cache of undelivered mail that sat patiently in a trunk. The letters arrived at the home of postmaster and postmistress Simon and Marie de Brienne in The Hague. Their trunk of undelivered mail, The Brienne Collection, presented a golden opportunity for the international team of researchers to scan and reconstruct a 3D model of the locked letterpackets.

“We were not interested in working on the project if the endgame was to tear open the unopened letters,” said Dambrogio. “The unopened letterpackets preserve invaluable letterlocking evidence that helped us to prove some of the letterlocking categories presented in our first ever categorization of locked letters.”

Thanks to the different layers in the folded paper, the research team’s algorithm is able to distinguish between ink and paper. The whole process gives a glimpse into the letter, the locking process and something else — a peek into a different time and a different way of life.

Computer-generated unfolding animation of sealed letter DB-1538. Researchers used “virtual unfolding” to read the contents of sealed letters from 17th-century Europe without physically opening them. (Unlocking History Research Group)

“The people whose lives are recorded in the Brienne trunk were ordinary people in extraordinary circumstances — often separated from their friends, families, and patrons for reasons of religious persecution, or simply the enduring need to make money,” said Dambrogio. “These letters poignantly capture their attempts to maintain vital human connections across vast and sometimes dangerous distances.”

As for Sennacques’ letter, the study offers a glimpse into a failed attempt to sort out paperwork related to a death. The pang of someone not receiving a message is a universal feeling, but 300 years ago Sennacques probably remained unaware for some time his message was sitting at the bottom of a trunk in the Netherlands, undelivered and unread.

“Lawyers today might sometimes have trouble reaching their clients — but in early modern Europe, it was always a possibility that your letters would never be delivered,” said Dambrogio.

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