Mathematical wrinkles for teachers and private learners ..
A 1912 mathematics teaching book by Samuel Isaac Jones, published by himself in Gunter, Texas, for teachers and private learners. Its pictures are plain geometric line diagrams: a Pythagorean-style figure of squares on a triangle, a star made of straight and dashed lines numbered at its points, and angled construction figures with lettered vertices. A designer could take from them the clean, schematic look of technical line drawing with lettered labels and dashed construction lines.
