Texts on architecture have been written since ancient time. These texts provided both general advice and specific formal prescriptions or canons. Some examples of canons are found in the writings of the 1st-century BCE Roman Architect Vitruvius. Some of the most important early examples of canonic architecture are religious.
 What is an insignificant early architectural canonical type? (If the question is unanswerable, say "unanswerable")
unanswerable