1914 – Solid 3D Curves for Engineering

In his 1914 book, Brinton discusses various techniques for building solid models of three-dimensional charts and functions for the purposes of engineering, and uses the two designs above as examples. Although these don't look like they could be solid models, the text from Brinton's book suggests they are. The first one (left) is made of plaster and shows the characteristics of a light bulb. The second (right) is made of cardboard and shows the results of tests of a fan. The two artifacts are undated.

Source: Brinton (1914) Graphic Methods for presenting facts, pp 335-337.