The shift in Westerners' perception of space was not as dramatic as the change in their perception of time. There was no jackrabbit start like the invention of the mechanical clock. Giovanni Tortelli, writing circa 1450 about all the new things that were transforming his world – the clock, compass, pipe organ, sugar, tallow candle – mentioned only one pertaining to the measurement of extension, a new kind of maritime chart, the portolano, and allowed that he was not as impressed with it as the others because “it is the work of long labors and careful diligence rather than of a divine challenge.” The transformation in Western perception of space, which culminated in changes as radical as those that shook physics at the beginning of the twentieth century, started like a tortoise.

The compass, acquired from Asia early in the second millennium, persuaded sailors to risk the long run from Cape Finisterre to England or across the Mediterranean in winter when clouds covered the pole star. They needed, of course, to be sure of the correct compass course, and for that it would be convenient to have charts, that is, accurate drawings of bodies of water and of the surrounding coasts in relation to each other, with indications of the shortest compass courses between the most prominent features, visually and commercially, of those coasts.