Designed by Wilhelm Segerblom in the late 1800's.
(three wood pieces, 2.25 inches)
IBM Burr page
cites the April 1899 issue of
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.
IBM Burr Page,