a blank sheet of paper

'It often happens that we look at a dress, a tapestry, or a blank sheet of paper so absentmindedly that we do not immediately perceive a shape or glittering spot thereupon that later strikes our eye all of a sudden, as if it had appeared there at the very moment we noticed it.'

'Balzac, from Le Bal de Sceaux. As quoted in Optiques: the science of the eye and the birth of modern French fiction by Andrea Goulet, 2006.