Most puzzle enthusiasts are familiar with burr puzzles as a special category of interlocking puzzles, traditionally made out of wood. They consist of a set of sticks with carefully aligned notches that allow them to interlock to make a three-dimensional shape that conceals the notches. But where did these puzzles start? And why are they called burrs? The origin story is itself a mystery, with clues going back at least three centuries. The earliest known record of such a puzzle is from a 1698 engraving used as a title page of Chambers's Cyclopaedia. Shown there as part of a huge panorama of scientific and mathematical devices, it appears it had already acquired popularity among scholars. This is the Chinese Cross Puzzle ("Luban Suo") that now called a burr puzzle or the six-piece burr puzzle (You can see a six-piece burr in the lower left side on the image below). The burr heritage includes magic as well as science. Illusionists frequently accomplish “impossible” penetrations of solid objects passing through each other, and many burr puzzles achieve the same illusion and are based on the same basic principles. In 1733 Pablo Minguet y Irol included the classic six-piece burr in Engaños à Ojos Vistas (English translation: Deceptions in Plain Sight). In Berlin, a German toymaker named Peter Friedrich Catel included ads for two burr puzzles in his 1785 catalogue of educational wonders for children. Dramatically called “devil’s hooves,” one of these had six pieces and the other twenty-four, but we don’t know if Catel’s six-piece version was the classic arrangement or a variation.
Catel’s work also marks one of the earliest examples of how the puzzles have proliferated to create variations and subcategories. His twenty-four piece version was of the “cage” variety--i.e. it had an object locked inside it--so we know that version goes back at least this far. Another early variation on the theme is the Cross Knot, which was depicted in the Magician’s Own Book in 1857 and in The Boy's Own Toymaker by Landells in 1859, where it was called the Chinese Cross. It was traditional at the time to attribute curios and oddities to the “mysterious east,” but some of the puzzles actually had a Chinese influence: one variation on the six-piece burr appears in 1889 in a compilation of Chinese magic by Tang Yunzhou.
A traditional six-piece burr appeared in 1893 in Hoffmann's Puzzles Old and New as "The Nut (or Six-piece) Puzzle." The name “nut” may be a forerunner of the eventual name “burr,” as both of them refer to the finished puzzle’s resemblance to part of a plant. Unfortunately, we don’t know who coined the current name; a pair of US patents were filed between 1915 and 1918, covering the classic six-piece burr and Chinese Cross, but neither used the categorical term. The earliest recorded use of the term “burr puzzle” is in the book Puzzles in Wood by Edwin M. Wyatt in 1928. Wyatt sometimes gets credit for coining the term, but his context there strongly suggests that it was already in common use.
Whether Wyatt coined the name or not, he defined the category, gathering together fifteen variations on the six-piece burr, and several others that shared that distinctive resemblance to seed burrs. These included the three-piece burr puzzle, which was also the simplest form of the “pagoda” category. One that Wyatt dubbed the “Three-Piece Cross” would be seen in later puzzle books identified by the C.C.O shapes of the pieces. Wyatt also added the Altekruse Puzzle (the name means “old cross” in German), first patented in 1890, calling it "The Twelve Piece Burr." Possibly his greatest contribution was a notation system for burr pieces, borrowed from Arthur L. Smith’s article on burr puzzles in Popular Science two years prior. With this system, burr puzzles officially entered the realm of mathematics, and the puzzle world would never be the same again.
Of Wyatt’s fifteen, four had the hollow spaces that lent themselves to increasing levels of complexity, and future generations responded with enthusiasm. Fans started measuring the “level” of a burr puzzle by the number of steps to remove the first piece, and whether or not the solution was unique. They spoke of the differences between “solid” and “holey” burrs, and the various virtues of each. When Anthony S. Filipiak published 100 Puzzles - How to Make and Solve Them in 1942, the six-piece burr held a place of honor as his personal favorite, and he had expanded Wyatt’s fifteen to a system for 73 distinct puzzles from just 38 pieces. Thirty-three years later, Bill Cutler began an exhaustive computer analysis of possible burr models that predicted hundreds more possibilities that have yet to be created.
Along the way, the category has expanded in range as well as depth. Willem van der Poel contributed the first 18-piece 6x6x6 burr in 1951, now known as the Grandfather Burr Puzzle more due to its amount of pieces than age (it was the first 18 piece burr puzzle). The proliferation continued, with pagodas expanding into their own subcategory that includes the 24 piece burr called "Chuck" designed by Edward Nelson. Many other interlocking puzzles have since been adopted into the family, including some Japanese interlocking puzzles called Kumiki Puzzles like Dinosaur Egg and Ball Puzzle which lack the burr’s distinctive spines, and the Diamond Puzzle which all pieces have notches.
Whether you prefer a set like Filipiak’s or the newest novelty, there is a wide variety of options these days, as the “family” of burr puzzles is keeping adds new children, cousins and in-laws. Whoever they were, we owe a debt to the nameless pioneers who started it all, when they looked at a few pieces of wood and saw something that could mystify, frustrate, instruct and amaze. Like the serpent in Shaw’s Back To Methuselah, they dreamed of things that never were, and said: “Why not?”
And our world is all the richer for it.
If you want to try designing your own Burr Puzzle or to learn more about the mathematics and the engineering behind the burr puzzles, I recommend the Burr Tools. It's a great free program that allows you to find all the solutions for nearly any puzzle that is assembled out of dice shaped units and create your own 3D interlocking puzzles. http://burrtools.sourceforge.
Jerry Slocum, from his book “New Findings on the History of the Six Piece Burr"
Stewart T. Coffin, from his books "Geometric Puzzle Design " and "The Puzzling World of Polyhedral Dissections"
Rob's Puzzle pages archive http://www.robspuzzlepage.com/interlocking.htm
Photos of the Chambers, Ephraim https://uwdc.library.wisc.edu/collections/HistSciTech/Cyclopaedia/