Calibron Twelve Block Puzzle (Calibron 12)

The [Calibron Twelve Block Puzzle](http://webapp1.dlib.indiana.edu/images/item.htm?id=http://purl.dlib.indiana.edu/iudl/lilly/slocum/LL-SLO-023178) is an apparently simple bin-packing puzzle credited to Theodore Edison in 1933 and originally marketed by his company, Calibron. The goal is simply to arrange all the pieces so that they form a rectangle (hint: make a 56x56 unit square). However, difficulty of this puzzle is rated 5/5!

There have been a lot of variants of this puzzle; in fact, the