They were mounted on powerful mustangs, which, with proper handling and judicious rests, could go on forever.

But they pushed them a little that afternoon, stopped for two hours after sundown, and then went on again.

They crossed the Colorado River in the night, swimming their horses, and about a mile further on stopped in dense chaparral.
They tethered the mustangs near them, and spread out their blankets.
"If anything comes the horses will wake us," said Smith.
"I reckon they will," said Karnes.
Both were fast asleep in a few minutes, but they awoke shortly after sunrise.

They made a frugal breakfast, while the mustangs had cropped short grass in the night.

Both horses and men, as tough and wiry as they ever become, were again as fresh as the dawn, and, with not more than a dozen words spoken, the two mounted and rode anew on their quest.