An accurate method of measuring the moments of inertia of airplanes
This is a 1930 NACA technical note, published by the National Advisory Committee for Aeronautics in the United States, that sets out a method for measuring airplane moments of inertia, written for aeronautical engineers and researchers. Its pictures are precise line drawings of a suspended pendulum rig with dashed outlines of an airplane, labelled with axes and centres of gravity, plus one side view of a biplane hung from a cable; a designer could borrow their clean technical diagram style and the isometric framing of suspended objects.
