Etymology Whiz

File under: Delightful random email from a Fast Company reader, but I just received the following:

Could you provide a source for the claim that the phrase “Think Outside the Box” originiated as a management tactic/catchphrase?

Googling for the origin of the phrase, I came across a Web site that states:

The phrase think outside the box is an allusion to a well-known puzzle where one has to connect nine dots, arranged in a square grid, with four straight lines drawn continuously without pen leaving paper. The only solution to this puzzle is one where some of the lines extend beyond the border of the grid (or box). This puzzle was a popular gimmick among management consultants in the 1970s and 80s as a demonstration of the need to discard unwarranted assumptions (like the assumption that the lines must remain within the grid).

The term dates to at least to 1975.

Any more specific citations?

Update: My colleague Ryan Underwood — who has clearly read more of the June issue than I have so far — sheds additional light on the origin of the phrase.