NPR
Researchers from MIT and other institutions have successfully uncovered the letterlocking technique that Mary, Queen of Scots, used to seal her final letter, reports NPR’s Tien Le. “The spiral lock requires more than 30 steps and involves cutting out a ‘lock,’ often resembling a dagger or sword, out of the blank margin of the letter,” writes Le. “The lock acts as a needle and is sewn through the letter after folding it.”