> The boys’ father agreed to their cross-country ride and helped them plan the route. Abernathy postulated a few rules before they set out: They could not travel more than 50 miles in one day

I've done very long distance pack-horsing in wild places and these are indeed the big problems. There's this thing like the tyranny of the rocket equations.. a horse can't carry what it needs to drink, so you almost have to follow rivers or know exactly where they are and when you'll hit them. I came from long-distance cycling too where I would think nothing much of 100 miles on a good day even on trails, carrying food and water no problem. Not going to happen with horses on long solo trips without logistical support.. you can push limits for days without consequence but not for weeks