General theory of windmills
A 1923 technical report titled General theory of windmills, issued through the NASA Technical Reports Server and aimed at engineers studying wind turbine performance. Its single picture is a plain engineering chart, Fig. 2, plotting a ratio of velocities against a pressure coefficient Cp on gridded axes, with a smooth curve through marked data points. A designer could borrow its clean grid-and-curve layout for minimalist data graphics.
