Darwin said he thought better while walking

(From Robin Sloan) There’s a great bit from Robert MacFarlane’s book Old Ways, in which he writes that a wise man “told me once about how [Charles] Darwin had constructed a sandy path which looped through the woods and fields around his house at Downe, in Kent. It was while walking this path daily that Darwin did much of his thinking, and he came to refer to it as the “Sandwalk” or the thinking path. Sometimes he would pile a series of flints in a rough cairn at the start of the path, and knock one away with his walking stick after completing each circuit. He came to be able to anticipate, [the wise man] explained, a “three-flint problem” or a “four-flint problem”, reliably quantifying the time it would take to solve an intellectual puzzle in terms of distance walked.”