Algorithm opens sealed seventeenth-century letter

In a world first, an international team of researchers has read an unopened letter from the seventeenth century without breaking its seals. Using advanced scanning technology and a computational algorithm, the team was able to virtually open the letter. The team’s findings appear today in Nature Communications.

The team managed imaged the folded and sealed letter using X-ray microtomography, an advanced scanning technology. The X-rays reflected the iron particles in the ink, making the words visible. The letter was then virtually opened by a computer-controlled algorithm that pieced the scans together to create legible text. It took the researchers four years to develop the algorithm.


Algoritme opent verzegelde zeventiende-eeuwse brief

A seventeenth-century trunk with letters that belonged to postmaster Simon de Brienne (Courtesy of the Unlocking History Research Group archive).

Insight into ordinary people’s lives

As a result, the team was able to reveal the contents of the letter, hidden for more than three centuries. The letter was sent on 31 July 1697 by Jacques Sennacques to his cousin Pierre Le Pers, a French merchant in The Hague. Jacques asked for a certified copy of a death notice of one Daniel Le Pers. "This insight into the lives of ordinary people from the past is very rare. Usually, only the correspondence of elites is preserved and studied", says Rebekah Ahrendt of Utrecht University.


Algoritme opent verzegelde zeventiende-eeuwse brief

The sealed letter unfolded by the computer algorithm. The letter is part of the Brienne Collection, managed by Beeld en Geluid Den Haag. The letters were in the possession of a postmaster couple from The Hague who handled correspondence between the Netherlands and France. (Courtesy of the Unlocking History Research Group archive).

Innovation and collaboration

The project is ground breaking because scientists from completely different fields collaborated, explains David van der Linden of Radboud University. "Historians often use letters as a window on people’s past, but they’re also material objects. It is precisely because we collaborated with curators and computer scientists that we began to pay attention to the material features of letters."

Nadine Akkerman of Leiden University: "What we have achieved is more than simply opening the unopenable, and reading the unreadable. We have shown how interdisciplinary work breaks down boundaries to investigate what neither humanities nor the sciences can hope to understand alone.’ Ahrendt: ‘It is precisely this kind of multidisciplinary, multi-sensory work that will motivate all of our fields toward innovation."

Funded partly by a grant from the Dutch Research Council (NWO), humanities scholars from the Netherlands were able to work together on an interdisciplinary basis with computer scientists from MIT. The research team consists of Rebekah Ahrendt (Utrecht University), Nadine Akkerman (Leiden University/De Jonge Akademie), David van der Linden (Radboud University), Jana Dambrogio (MIT Libraries), Amanda Ghassaei (Adobe Research), Daniel Starza Smith (King's College London), Holly Jackson (MIT), Erik Demaine (MIT), Martin Demaine (MIT), Graham Davis (Queen Mary University of London) and David Mills (Queen Mary University of London).


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