People once folded their correspondence in intricate ways, known as “letterlocking,” to keep out snoops. A fancy new imaging technique sees right through it.
On July 31, 1697, Jacques Sennacques sent a letter to his cousin—one Pierre Le Pers, a French merchant living in The Hague—begging him, for the love of Pete (that’s paraphrased), to send him a death certificate for his relative, Daniel Le Pers. In a 17th century version of the dreaded “as per my previous email,” Sennacques wrote: “I am writing to you a second time in order to remind you of the pains that I took on your behalf.” Basically, you owe me
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