Three hundred years ago, before envelopes, passwords, and security codes, writers often struggled to keep secret the thoughts, worries, and dreams that were expressed in their letters.
One popular approach has been to use a technique called letter locking – the intricate process of folding a flat sheet of paper to make your own envelope. This security strategy presented a challenge when 577 blocked letters that were delivered to The Hague, Netherlands between 1689 and 1706 were found in a suitcase with undelivered mail.
The letters had never reached their ultimate recipients, and conservationists refused to open and damage them. Instead, a team found a way to read one of the letters without breaking its seal or unfolding it in any way. Using a highly sensitive X-ray scanner and computer algorithms, the researchers virtually unfolded the unopened letter.
This is a computer generated unfold sequence of a sealed letter from 17th century Europe. The virtual unfolding was used to read the contents of the letter without physically opening it. Recognition: Courtesy of the Unlocking History Research Group Archives
“This algorithm puts us right in the heart of a blocked letter,” the research team said in a statement.
“Sometimes the past defies scrutiny. We could have just cut open these letters, but instead we took the time to examine them for their hidden, secret and inaccessible properties. We have learned that letters can be much more revealing, if they are. ” left unopened. ”
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 notice of Daniel Le Pers.
The details may seem prosaic, but the researchers said the letter gives fascinating glimpses into the lives of ordinary people – a snapshot of the early modern world as it did its business.
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 by X-ray microtomography and virtually unfolded for the first time in centuries to reveal its contents. Recognition: Courtesy of the Unlocking History Research Group Archives
In addition to the unopened letters, it contains 2,571 opened letters and fragments that, for one reason or another, never reached their destination.
There was no postage stamp at the time, and the recipients, not the senders, were responsible for the postage and delivery charges. If the recipient passed away or refused the letter, no fees could be charged and the letters were not delivered.
A new way to dismantle historical documents
The X-ray scanners were originally developed to map the mineral content of teeth and have so far been used in dental research.
“We were able to use our scanners for 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 uses much more intense x-rays that allow us to see the tiny traces of metal in the ink that were used to write these letters. The rest of the team were then able to scan our images and turn them into letters, which they could virtually open 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 that contains a picture of a bird. Recognition: Courtesy of the Unlocking History Research Group Archives
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 says.
“Using virtual unfolding to read an intimate story that never saw the light of day – and has never reached its recipient – is truly extraordinary,” the researchers said in the statement.
The research was published Tuesday in the journal Nature Communications.