"Look out for toads with horns and tails." So read one of the many cautionary notes that William Clayton (1814-1879) recorded in this guide for Mormon pioneers who were embarking on the long and often treacherous journey westward to Salt Lake City, Utah. Clayton designed a "roadometer," an early odometer, to track the mileage from point to point. "About noon today Brother Appleton Harmon completed the machinery on the wagon called a "roadometer" by adding a wheel to revolve once in ten miles, showing each mile and also each quarter mile we travel, and then casing the whole over so as to secure it from the weather. We are now prepared to tell accurately, the distance we travel from day to day which will supercede the idea of guessing, and be a satisfaction not only to this camp, but to all who hereafter travel this way." (From William Clayton's journal; a daily record of the journey of the original company of "Mormon" pioneers from Nauvoo, Illinois, to the valley of the Great Salt Lake, 1921).