MIT News  March 2, 2021 Computational flattening algorithms have been successfully applied to X-ray microtomography scans of damaged historical documents, but have so far been limited to scrolls, books, and documents with one or two folds. An international team of researchers (US -MIT, industry, UK, the Netherlands) used automated computational flattening algorithm to read an unopened letter from early modern Europe without breaking its seal or damaging it in any way. They reconstructed the intricate folds, tucks, and slits of unopened letters secured shut with “letterlocking,” a practice—systematized in this paper—which underpinned global communications security for centuries before modern envelopes. […]