Sources page biographical material

6.AS.3.a. THREE EQUAL 'SQUARES' TO A HEXAGON
Catel. Kunst-Cabinet. Vol. 2, 1793. Das Parallelogramm, pp. 14-15 & fig. 249 a,b,c,d on plate XII. This shows three squares, each dissected the same way into 4 pieces which will make a hexagon or two equal equilateral triangles. Consider a hexagon and connect three alternate vertices to the centre. Join up the same vertices and drop perpendiculars from the centre to three of the sides of the hexagon. However, close examination shows that the squares have dimensions 3/2 by 3. The figure of the three adjacent squares has the divisions between them hard to make out.

Bestelmeier. 1801. Item 292/293 -- Das Parallelogram. Almost identical to Catel, except the diagrams are reversed, and worse, several of the lines are missing. Mathematical part of the text is identical.