Book: 'The Horse in Motion: As Shown by Instantaneous Photography. With a Study on Animal Mechanics, Founded on Anatomy and the Revelations of the Camera, in which is Demonstrated the Theory of Quadrupedal Locomotion', 1882. By J D B Stillman AM MD, using photographs by Eadweard Muybridge. Executed and published under the auspices of Leland Stanford. Illustrated with 5 heliotypes, showing positions of cameras and motion.
In 1872 photographer Eadweard Muybridge was asked to help settle an argument for the businessman Leland Stanford over whether a trotting horse lifts all four feet off the ground. He developed a new process for high-speed photography using 12 cameras pointed at a track marked with vertical lines. The horses triggered his electromagnetically controlled shutters by breaking thin threads as they passed.
Although simple silhouettes, his images proved that human vision could not see the reality of how a horse moved. This account was written by Stillman, Stanford’s physician, using Muybridge’s images.