Lonesome Dove, Volume 2: Comanche Moon by Larry McMurtry

LONG BEFORE Buffalo Hump came to the dry lake where the first people had lain in wait to catch the wild horses that came to refresh themselves at the little seeping spring, he wished he had used better judgment in picking a horse for his own last journey. The problem was that the old horse he had chosen had worn away all his teeth; in the canyon there was tall grass that he could masticate, but on the dry llano, in the vicinity of the Lake of Horses, there was no tall grass. The old horse was reduced to dirtying its nose as it tried to get at the sparse, short grass with its yellow nubs of teeth. Though the horse had frisked along briskly for some twenty miles, its strength soon gave out and it became what it was: an old horse slowly dying for lack of teeth. That was the way of old horses, just as shaky hands and wavery eyesight was the way of old men. Buffalo Hump knew he had made a poor choice. He wanted to reach Black Mesa, to sing his way into death among the black rocks that were the oldest rocks. Some believed that only in the black rocks were the spirits that welcomed one into death.

But, because the old horse had slowed to a walk, Buffalo Hump was still a long way even from the Lake of Horses. He knew, though, that if the little spring was still seeping, the old horse might refresh itself and make it on to Black Mesa.