Octavo used in a sentence

Octavo in a sentence as a noun

Is it important that a sheet of A4 paper is about one eighth of a square meter?And in defense of US Letter, its proportions are closer to the golden ratio than A4, which looks too skinny for me. But they're both too wide for letter writing; I think either octavo-sized or A5 paper is a more natural width for printing or hand-writing a single column of text.