Dalles octagonales - geometric perspective (double-sided)

Drawing on single leaf, 8.25 x 6.25 inches, text on verso. Loosely mounted in double-window acid-free mat and archival sleeve, 14 x 11 inches, viewable from either side. Very Good condition with light soil and edgewear, small old tape repair in the upper corner. From a mid-19th century French student manuscript on architectural and mechanical drafting containing notes for computational and perspective drawing, studies on light and shade, reflection, etc.A great articulation of structuring/tiling octagons with a tiny annotation on the method of determining their edges in the bottom corner. Done in red, blue, and brown inks with explanatory text on the verso. Wonderful detail.