A regular paced walk can finish a marathon - 26.2 miles - in 6-8 hours.
Before automation mankind worked sun-up to sun-down which would allow the fittest to easily cover 40-50 miles/day.
Not without stopping.
Marathon horses carry riders over 100 miles in the same time.
Endurance Rides (ERs), these are only for advanced horse and rider combinations. They are the hardest test for both. All FEI and International competitions are ERs, but there are also many ERs on the National calendar. They usually begin with a mass start, and the riders aim to cover the distance as fast as they can, taking into account the terrain and welfare of their horse. During the Ride the rider will be required to present their horse to the vet at various set intervals to be checked as fit to continue. Following this are rest periods called “holds” where the horse and rider can eat and take a breather before continuing. Many riders’ ultimate goal is the successful completion of an Endurance Ride. These vary from 80 –160 km in a day or longer over several days.
Endurance riding was first developed in the early 1900s as a military test for cavalry mounts. Horses were required to go on a 5-day, 300 mile (483 km) ride carrying at least 200 lbs. The cavalry test became a civilian sport in the early 1950s.