#1872

Nine Linked Rings (Baguenaudier) (1872) — The Year an Origin-Unknown Ring Puzzle Turned Out to Use Binary Math 81 Years Before a Telegraph Engineer Patented the Same Idea

Nine Linked Rings, or Baguenaudier: remove rings from a bar one at a time until the last one slides free. Its origin is said to be China, but nothing is settled; the earliest confirmed records are a 16th-century Chinese text and, around the same time, the writings of Italian mathematician Luca Pacioli. In 1872, Lyon mathematics enthusiast Louis Gros became the first to theorize the puzzle's solution as a binary table. The same idea was independently reinvented 81 years later, in 1953, when telegraph engineer Frank Gray patented what communications engineers now call the "Gray code." As a physical puzzle, a 1970 patent by William Keister became "Spin-Out," an early product of Binary Arts (founded 1985, now ThinkFun), still sold today. This piece follows the 150-year lineage of a single ring mechanism.