We recently came across a compelling blog post about letters sent home by Russian soldiers during World War II. Without access to envelopes and postcards, the soldiers folded up triangular letters that were their own package--”letter and envelope in one.” The folded format was necessary since mail needed to be reviewed by censors and couldn't be sealed. Although the letters are a great example of historical improvisation, we love the simple little how-to that accompanies the story - an…