Researchers ‘virtually unfold’ a 17th-century unopened letter

Before envelopes were commonly available, people used to use “letter-locking” to seal their messages from prying eyes — that’s when you fold a piece of paper in such a way that it becomes, essentially, its own envelope. Using high-tech scanning and a computer algorithm, a team of multidisciplinary researchers has “virtually unfolded” one such sealed letter, written in the 17th century but never opened. The World’s Amanda McGowan has the story.