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A New Scientific Technique Has Revealed the Secret Contents of a 300-Year-Old Letter

Researchers can now read "locked" letters without opening them.

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  • The Brienne Collection of locked letters.Photo Credit: Sound and Vision The Hague / Massachusetts Institute of Technology

A recent virtual-reality breakthrough will offer researchers the ability to read letters that were sealed centuries ago—without ever opening or unfolding their delicate pages. The fascinating new technique has already been used to reveal the never-before-seen contents of a "locked" letter sent in 1697.

Dating back to the 13th century, the practice of letterlocking allowed senders to protect the contents of their letters by intricately folding, tucking, and sometimes even sewing the pages in on themselves. As envelopes were not widely accessible until the 1830s, these careful methods of concealment ensured that messages remained private until they reached their intended recipient.

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While some historic letters have been cut open for study, a new technique developed by a team of 11 scientists and scholars at M.I.T. will help researchers virtually unfold messages, without the risk of damage. Using advanced X-rays designed for dental applications, researchers can now scan letters, digitally unfold them, and use a computer to read what's inside. 

This technique provides researchers the opportunity to examine the contents of many previously unread letters. To demonstrate the efficacy of the newly-developed technology, a team of scholars virtually opened four letters written between 1680 and 1706. One such letter, dated July 31, 1697, was sent from a Jacques Sennacques to his cousin, French merchant Pierre Le Pers. In it, Sennacques requests a certified copy of Daniel Le Pers' death notice.

The four virtually-opened letters were among 577 other locked letters found in a trunk that is now part of the Brienne Collection at The Hague. The trunk once belonged to Simon de Brienne and his wife Marie Germain, who served as postmaster and postmistress. 

It is believed that many of the letters found in this trunk were being stored there because they could not be delivered. Before the advent of postage stamps, those who received a letter had to pay for its delivery. However, this practice caused some letters to go undelivered, especially if a recipient refused to pay or couldn’t be located.

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Beyond the many locked letters of the Brienne Collection, which researchers hope will reveal insights about early modern Europe, other similar collections will likely benefit from the newly-publicized X-raying technique. Some are already hoping to see scans of the Prize Papers, an archive of documents that were taken from British enemies between the 1600s and 1800s and are potentially brimming with secrets. 

The new technique will also help researchers learn more about letterlocking as a practice. Instead of destroying folding patterns to discover what's inside a letter, researchers can extract its content and further study the methods of letterlocking used. One such discovery was already made by the scholars who worked on this project. After examining 250,000 letters and organizing letterlocking methods into broad formats and categories, they found that folding techniques varied widely from person to person, akin to a unique signature.

Opening the door for future discoveries, this technique of virtual unfolding holds the promise of revealing exciting new insights into the past.