Today the postman brought two small sized Extreme Torture Puzzles that I have purchased from flickr-member fibra, who is quite a tinkerer - recently I posted about his homebuilt Cracklebox on Mocking Minority's Blog.
Lasercut from acrylic, this extremely sophisticated puzzle consists of 6 pieces, which have to be assembled (or rather taken apart) three-dimensionally.
The Extreme Torture Puzzle was found by dutch mathematician Frans de Vreugd around 2002, who used software to search for ever-new configuations, starting from the so-called 6-board burr puzzle, which has been around since the start of the 19th century.
(pic: de Vreugd's Irregular Board Burr, with a "level-184.108.40.206.3" solution)
"Extreme Torture requires 28 moves to remove the first piece, then 21 moves to remove the next piece, for an incredible level-28.21 solution. This is at the far-limits of human solvability. After finding these unexpected complexities within simple pieces, the whole field is opening up to more searches."
Being single-colored, there are 8 ways to assemble fibra's version, in contrast to a multi-colored version ... still I'm not sure I want to dare taking one apart, as I consider using them as presents ...