From astronomy we find the east, west, south, and north, as well as the theory of the heavens, the equinox, solstice, and courses of the stars. If on… - Vitruvius

Pytheos made a mistake by not observing that the arts are each composed of two things, the actual work and the theory of it. One of these, the doing of the work, is proper to men trained in the individual subject, while the other the theory is common to all scholars.

The elm and the ash... when put in shape for use in buildings... are tough and having no stiffness... soon bend. But when they become dry with age, or are allowed to lose their sap... they get harder, and from their toughness supply a strong material for dowels to be used in joints and other articulations.

Dimension stone, flint, rubble, burnt or unburnt brick,—use them as you find them. For it is not every neighborhood or particular locality that can have a wall built of burnt brick like that at Babylon, where there was plenty of asphalt to take the place of lime and sand, and yet possibly each may be provided with materials of equal usefulness so that out of them a faultless wall may be built to last forever.