Segerblom Knot

Designed by Wilhelm Segerblom in the late 1800's.
(three wood pieces, 2.25 inches)

The IBM Burr page cites the April 1899 issue of Scientific American as publishing this puzzle. Three identical pieces each have outer dimensions 2 by 2 by 6 units. Each has all of the center 2 by 2 by 2 portion removed except for a 1 by 1 by 2 rod that is beveled at 45 degrees (a total of 7 units of wood has been removed from each piece). To assemble, all three pieces have to be slid together simultaneously (an outside surface of the rod slides perpendicular to one piece while the beveled surface slides over the corner of another). It is not possible to put two pieces together and then slide the third one in. The figure below shows the three identical pieces in the orientation to be put together.

Further reading:
IBM Burr Page, from: