105. There are no instruments for measuring color; there are no ‘color thermometers’. How could there be, as ‘color knowledge’ always remains contingent upon an individual perceiver? This didn’t stop a certain Horace Bénédict de Saussure, however, from inventing, in 1789, a device he called the ‘cyanometer’, with which he hoped to measure the blue of the sky.

106. When I first heard of the cyanometer, I imagined a complicated machine with dials, cranks, and knobs. But what de Saussure actually ‘invented’ was a cardboard chart with 53 cut-out squares sitting alongside 53 numbered swatches, or ‘nuances’, as he called them, of blue: you simply hold the sheet up to the sky and match its color, to the best of your ability, to a swatch. As in Humboldt’s Travels (Ross, 1852): ‘We beheld with admiration the azure colour of the sky. Its intensity at the zenith appeared to correspond to 41° of the cyanometer.’ This latter sentence brings me great pleasure, but really it takes us no further – either into knowledge, or into beauty. – Bluets, Maggie Nelson