Accordingly, let the atrium be viewed as a quadranglar shape, whose center is the earth and the eye. Of the four corners let one be east, the one opposite west. Of the two remaining corners diametrically opposite, let one wear the label of the north, the other of the south. In the four spaces in between, that lie in the middle of the sides or walls, let east, west, north and south be indicated.
Thus you have eight distinct points and places first, each of which should determine for itself two collaterals [or secondary lines], that is, right and left, then east’s right and left, west’s right and left, and so on with the remaining spaces. In the same way the east corner’s right and left, the west corner’s right and left, and so on with the remaining corners.