In one episode of the adult cartoon Rick and Morty, drunken scientist, Rick, derides his grandson, Morty, for imagining that he can put up shelves using his ‘sad, naked caveman eyeball’ and a ‘bubble of air’ – that is, using a spirit level. He decides to demonstrate ‘true level’, and uses a variety of arcane devices to even out a square of the garage floor to improbable flatness. Stepping, for the first time ever, onto a ‘truly level’ surface, Morty’s reaction is close to rapture, and when he is dragged back out of the square, he is anguished: ‘Everything is crooked! Reality is poison!’

Simon Winchester had a surprisingly similar formative experience, only without the drunkenness and anguish. One day in the mid-1950s, when Winchester was a child, his father brought home a box containing a large number of steel tiles. Although they were not magnetic, these tiles were polished to such