170 years ago today - May 8, 1847. Saturday.

[William Clayton]
I have counted the revolutions of a wagon wheel to tell the exact distance we have travelled . . . I found the wheel 14 feet 8 inches in circumference, not varying one eighth of an inch. I then calculated how many revolutions it would require for 1 mile and found it precisely 360 not varying one fraction which somewhat astonished me. I have counted the whole revolutions during the days travel and find it to be a little over 11 1/4 miles, (20 revolutions over.) The overplus I shall add to the next days travel. According to my previous calculations we were 285 miles from winter quarters this morning before we started. After traveling 10 miles placed a small Cedar post in the ground with these words wrote on it with a pencil. "From Winter Quarters 295 miles, May 8, 47. Camp all well. W Clayton." Some have past the days travel at 13 and some 14 miles, which serves to convince more strongly that the distances are overrated. I have repeatedly suggested a plan of fixing machinery to a wagon wheel to tell the exact distance we travel in a day, and many begin to be sanguine for carrying it into effect, and I hope it will done...

[Source: George D. Smith, An Intimate Chronicle; The Journals of William Clayton, Signature Books in association with Smith Research Associates, Salt Lake City, 1995, http://bit.ly/WilliamClayton]