Affinograph
Oswald Gottlieb Coradi
1915
Imagine you are a civil engineer planning a long stretch of highway or railway. One major part of planning is to describe all the slopes, peaks and valleys of your design over possibly hundreds of miles. To fit a side-view drawing illustrating the slopes on a single sheet of paper, the relative differential between the high points and low points would be narrower than your pencil point. To solve this problem, engineers draw sections (side-views) of roads with two different scales for the horizontal (x) and the vertical (y) axis. The X is compressed and the Y is exaggerated to help illustrate the key design points. This can be a laborious drafting process. Enter the Affinograph, which can draw the X and Y axes at different ratios based on user parameters.
From the catalog: "The instrument shown in the above illustration is intended for reducing and enlarging the ordinates of curves in given ratios as desired; for instance for giving a uniform width of constants to curves of the same kind, but originating from different indicators, in order to facilitate the comparison. The instrument is also an Ellipsograph; if the one pin describes a circle then the other pin draws an ellipse in proportion to the reduced or enlarged ordinates.
In the x-direction the instrument can travel to any desired length: in the y-direction the guide pin can travel to a maximum length of 33cm (13")."
Mathematical-Mechanical Institute G.Coradi Zurich, Catalogue of mathematical precision instruments, 1915