Over 600 years ago, someone complexly folded, sealed and posted a letter that was never delivered. Now, scientists have digitally “unfolded” this and other similar blocked letters found in a 17th century chest in The Hague, using X-rays.
For centuries, before the invention of sealed envelopes, sensitive correspondence was protected from prying eyes by means of complex folding techniques called ‘letterlocking’, which transformed a letter into its own secure envelope.
However, blocked cards that survive to the present are fragile and can be opened physically only by cutting them into pieces.
The new X-ray method offers researchers a non-invasive alternative, maintaining the original folded shape of a pack of letters.
For the first time, scientists have applied this method to “locked” letters from the Renaissance period, kept in a chest that had been in the collection of the Dutch postal museum in The Hague, Holland, since 1926.
Computer generated scrolling animation of sealed letter DB-1538. (Unlock history research group file)
Related: Photos: 17th-century closed-card treasure
The contents of the chest include more than 3,100 undelivered letters, of which 577 were closed and blocked. Known as the Brienne Collection, the letters were written in Dutch, English, French, Italian, Latin and Spanish.
For unknown reasons, once the missives arrived in The Hague, they were never delivered to the intended recipients and were instead maintained by a postmaster named Simon de Brienne, Live Science previously reported.
Blocked cards used different mechanisms to remain securely closed, including folds and rolls; cracks and holes; folds and adhesives; and a variety of smartly constructed locks, according to a study published online March 2 in the newspaper Nature Communications.
To penetrate the layers of folded paper, the study authors used an X-ray microtomography scanner designed in the dental research labs at Queen Mary University of London (QMU).
The researchers designed the scanner to be exceptionally sensitive so that it could map the mineral content of the teeth, “which is invaluable in dental research,” said study co-author Graham Davis, professor of 3D X-ray imaging at QMU in an announcement.
“But this high sensitivity also made it possible to resolve certain types of ink on paper and parchment,” added Davis.
The chest was filled with sealed letters. (Unlock history research group file)
“The rest of the team was able to take our raster images and turn them into letters that they could virtually open and read for the first time in more than 300 years,” study co-author David Mills, facility manager for ray-microtomography facilities. X at QMU, said in the statement.
From the scans, the team built 3D digital reconstructions of the letters and then created a computational algorithm that deciphered the sophisticated folding, crease by crease techniques, opening the letters virtually “while preserving the evidence of letterlocking”, according with the study.
Scientists digitally opened four letters using this innovative method, deciphering the contents of one letter, DB-1627.
Written on July 31, 1697, it was written by a man named Jacques Sennacques for his cousin Pierre Le Pers, who lived in The Hague. Sennacques, a legal professional in Lille, France, requested the official death certificate from a relative named Daniel Le Pers, “perhaps due to an inheritance issue,” the scientists wrote.
“With the request issued, Senaques spends the rest of the letter asking for news from the family and recommending his cousin to the graces of God,” wrote the authors. “We don’t know exactly why Le Pers did not receive the letter from Senaques, but given the itinerant merchants, it is likely that Le Pers has changed.”
(Unlock history research group file)
Tens of thousands of sealed documents can now be unfolded and read virtually, the researchers reported.
“This algorithm takes us right to the heart of a closed letter,” said the research team in the statement. “Using virtual scrolling to read an intimate story that never saw the light of day – and never reached its intended recipient – is truly extraordinary.”
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This article was originally published by Live Science. Read the original article here.