Night writing
Night writing, AKA sonography, was a system of code that used symbols of twelve dots arranged as two columns of six dots embossed on a square of paperboard, and is now remembered as the forerunner of Braille. It was designed by Charles Barbier in response to Napoleon's demand for a code that soldiers could use to communicate silently and without light at night. Called sonography, each grid of dots stands for a character or phoneme.