Frans van Schooten's Exercitationes mathematicae

This is page 167 from the Exercitationes mathematicae (1657) of Frans van Schooten (1615-1660).  This book contained a collection of mathematical construction problems, among much else.  It was one of the books read by Isaac Newton while he was a student at Cambridge University and helped to introduce him to modern mathematics.  On this page we see a construction enabling one to find the distance across a river.

From the Rare Book and Manuscript Collection at Columbia University.

Part of the Mathematical Treasures section of Loci: Convergence.