If you guessed Odometer, you're right!
In 1847, William Clayton was tasked with collecting information of the first company of LDS pioneers as they journeyed west. This would help the next groups of pioneers as they traveled. His first attempts of estimating the mileage were ineffective and often differed up to 4 miles compared with other members.
"On 8 May 1847, near the site of present-day North Platte, Nebraska, Brother Clayton tied a marker on the spoke of his measured wheel (some sources say it was a piece of red flannel) and walked beside it all day long, tallying each rotation. He tells us frankly that the method was “somewhat tedious.” At the end of the day he had tallied 4,070 rotations." - Gospel Doctrine Manuel (My Kingdom Shall Roll Forth)
William Clayton recorded in his journal: I walked this afternoon in company with Orson Pratt and suggested to him the idea of fixing a set of wooden cog wheels to the hub of a wagon wheel in such order as to tell the exact number of miles we travel each day. He seemed to agree with me that it could be easily done at a trifling expense.
Designed by Orson Pratt and developed by Orson Pratt, William Clayton, and Appleton Harmon, this wooden odometer was a game changer for the trek west. It was first used on May 16, 1847 and was attached to the wagon of Heber C Kimball.
For more on this story, check out this article from LDS.org and this one!
Shared with permission.