Lösung Das war doch einfach, oder.

Thinking outside the box: The nine dots puzzle is much older than the slogan. It appears in Sam Loyd’s 1914 Cyclopedia of Puzzles. In the 1951 compilation The Puzzle-Mine: Puzzles Collected from the Works of the Late Henry Ernest Dudeney, the puzzle is attributed to Dudeney himself. Sam Loyd’s original formulation of the puzzle entitled it as Christopher Columbus’s egg puzzle.

The puzzle proposed an intellectual challenge—to connect the dots by drawing four straight, continuous lines that pass through each of the nine dots, and never lifting the pencil from the paper. The conundrum is easily resolved, but only by drawing the lines outside the confines of the square area defined by the nine dots themselves.

The phrase „thinking outside the box“ is a restatement of the solution strategy. The puzzle only seems difficult because people commonly imagine a boundary around the edge of the dot array. The heart of the matter is the unspecified barrier which is typically perceived.“