3 ideas
Palladio lists seven preferred room shapes: the circle, the square, and rectangles whose length equals the diagonal of the square on the width, or runs 1⅓, 1½, 1⅔ or 2 times the width. Vault heights come from arithmetic, geometric or harmonic means of length and width. Because each room is fixed by a ratio, the plan's proportions stay the same at any size and read as consonant, like musical intervals.
Every building is shown as a scaled orthographic plan and elevation with dimensions written on the plate. Placing his own villas next to measured Roman temples in the same format presents the new work as the same kind of thing as the ancient work, so the drawing itself becomes the proof of legitimacy.
Palladio argued that the ancients first put the pediment and portico on houses, and only later carried them over to temples. Putting a columned temple front on a farmhouse was therefore a return to the original use, not a borrowing. The portico also marks the main entrance, gives the owner dignity, and joins a central block to the working farm wings in one symmetrical composition.