> It's interesting that all lines in the sketch are straight, and circles are perfect, so it seems Whitfield took a ruler and a compass on that plane.

Imagine trying to board a plane with a compass nowaday :)

> ruler and compass

Or a circle template (rectangular with holes of different sizes). That would aid drawing the small circles, as well as drawing straight edges and right angles. It can be kept in a notebook like a bookmark.

On page 12 there's an ad for the cleanroom, and one of the selling points is that it would allow cigarette smoking!