Three hundred years ago, before envelopes, passwords, and security codes, writers often struggled to keep private thoughts, concerns, and dreams expressed in their letters.
One popular way was to use a technique called letter locking – the complicated folding of a flat sheet of paper to become its own envelope. This security strategy posed a challenge when 577 locked letters delivered to The Hague in the Netherlands between 1689 and 1706 were found in a trunk of undelivered mail.
The letters had never reached their ultimate recipients, and conservationists didn’t want to open and damage them. Instead, a team has found a way to read one of the letters without breaking the seal or unfolding it in any way. Using a highly sensitive X-ray scanner and computer algorithms, researchers virtually unfolded the unopened letter.
This is a computer generated unfolding sequence of a sealed letter from 17th century Europe. Virtual unfolding was used to read the contents of the letter without opening it physically. Credit: Courtesy of the Unlocking History Research Group archive
“This algorithm takes us to the heart of a closed letter,” the research team said in a statement.
“Sometimes the past resists criticism. We could have just cut these letters open, but instead we took the time to study them because of their hidden, secret and inaccessible properties. We have learned that letters can be much revealing when unopened abandoned. ”
The technique revealed the contents of a letter dated July 31, 1697. It contains a request from Jacques Sennacques to his cousin Pierre Le Pers, a French merchant in The Hague, for a certified copy of an obituary of Daniel Le Pers.
The details may seem prosaic, but the researchers said the letter provides a fascinating insight into the lives of ordinary people – a snapshot of the early modern world as it was going on.
This 17th-century suitcase with undelivered letters was bequeathed to the Dutch Postal Museum in The Hague in 1926. A letter from this suitcase was scanned with X-ray microtomography and unfolded virtually to reveal its contents for the first time in centuries. Credit: Courtesy of the Unlocking History Research Group archive
In addition to the unopened letters, it contains 2,571 opened letters and fragments that, for one reason or another, never reached their destination.
At that time there was no such thing as a postage stamp and the recipients, not the senders, were responsible for the postal and delivery costs. If the recipient died or the letter was rejected, no charges could be collected and the letters would not be delivered.
A new way to mine historical documents
The X-ray scanners were originally designed to map the mineral content of teeth and have been used in dental research to date.
“We’ve been able to use our scanners to make X-ray history,” study author David Mills, a researcher at Queen Mary University in London, said in a statement.
“The scanning technology is similar to medical CT scanners, but with much more intense X-rays, allowing us to see the minute traces of metal in the ink used to write these letters. The rest of the team was then able to take our scan. and turn them into letters that they can open virtually and read for the first time in over 300 years. “
The letter contains a message from Jacques Sennacques dated July 31, 1697 to his cousin Pierre Le Pers, a French merchant. Also visible is a watermark in the center with a picture of a bird. Credit: Courtesy of the Unlocking History Research Group archive
The new technique has the potential to unlock new historical evidence from the Brienne tribe and other collections of unopened letters and documents, the study said.
“Using virtual unfolding to read an intimate story that has never seen the light of day – and never even reached the recipient – is truly extraordinary,” the researchers said in the statement.
The research was published Tuesday in the journal Nature Communications.