Using computer algorithms and an X-ray scanner designed for dental research, an international team of researchers has unraveled the secrets of a folded letter sealed since 1697 – without opening it.
The “virtual unfolding” of the letter – the culmination of a four-year project described in an article published Tuesday in the journal Nature Communications – points to a new line of historical research into the age-old practice of letterlocking. That’s the term used to describe the use of origami-like folds to hide the contents of letters before envelopes were widely used in the mid-1800s.
“This is a conservation dream come true,” said Jana Dambrogio, the curator of the Massachusetts Institute of Technology Research Library and one of the paper’s eleven authors.
Experts say the technique used to reveal the text of the letter, including a type of imaging called X-ray microtomography, may also have applications in healthcare and engineering.
Letter locks varied in complexity depending on the expertise of the sender and receiver and how tamper-resistant they wanted their messages to be in transit. Some involved dozens of folds, resulting in packs the size of playing cards.