I just came across a charming story in Air & Space magazine. It’s by Don Piccard, an American balloon pilot and member of the Piccard dynasty of Swiss balloonists. He writes about this time in 1947 when he flew a Japanese balloon across a bit of Minnesota.  It was made from mulberry bark paper and had carried a bomb across the Pacific during the war. The Japanese sent 9,000 balloon bombs off in this direction, but they didn’t quite work out as planned.