Historically, the science of grading developed with the advent of the tape measure, the introduction of scientific tailoring systems, commercial patterns and the mass-production of pattern-built clothing in the 19th century. To properly fit a pattern to a range of sizes, each piece needed to be graded, meaning systematically increased or decreased. A German mathematician Dr. Henry Wampen wrote two influential works, "The Mathematical Art of Cutting Garments According to the Different Formation of Men's Bodies"(1834) and "Mathematical Instructions in Constructing Models for Draping the Human Figure"(1863). Wampen introduced the principle of gradation via these works. "The Mathematical Art" was translated into English by J. Happle-Hutcheson as "Dr. Wampen's World Renowned System of Anthropometry as Simplified and Americanized" in 1842, and remained in print into the 20th century