While my wife and I were visiting our son Clain and, incidently, our new granddaughter in Bozeman, MT, we visited the Museum of the Rockies in Bozeman. The Museum is most notable for its displays of dinosaur fossils. Right now they have a display of machines designed by Leonardo daVinci. Very few of his machines were ever built in his lifetime. The machines on display were made in recent years from the designs in daVinci's notebooks.
A number of his designs involved war machines because his salary was being paid by counts who were often at war.
The machine that caught my eye was Leonardo's machine for measuring distance. I think you'll get a kick out of it. It kept track of distance by dropping marbles (or pebbles) into a box as the mechanism moved along.
It doesn't mention how often one would have to reload the marbles but it would seem like it would have to be very often.
When the exhibit in Bozeman is over, maybe they would loan the device to someone to measure a Marathon!
Here are some photos: Leonardo's measuring machine
Alan