Canyon maybe this is what you were referring to…

From The Indians of Texas, From Prehistoric to Modern Times by W. W. Newcombe, Jr (Ninth Paperback Edition, 1990):

Chapter 7 Comanches: Terror of the Southern Plains, page 172-173
When an elderly person was obviously approaching death he was apt to be "thrown away" by his friends and relatives, not for want of affection but out of fear of evil spirits and his possibly malevolent soul. His kinfolk simply abandoned him. When a man was dying but had still some physical strength, he gave away his property and retired to an isolated spot to await death. He might take his own life after making the proper and final arrangements with his personal guardian spirits. Burial took place as soon after death as possible. Near relatives or close friends prepared the corpse with care, men attending to men and women to their own. The corpse was bathed, the face painted red, and the eyes sealed shut with clay. It was dressed in fine clothing, some of it donated by friends and relatives. The knees of the body were drawn up to the chest, the head was bent forward on it, and the flexed body was tied in this position. A blanket was wrapped and tied around the body which was then placed on a horse. Women, riding on either side or behind the corpse, took it to the place of burial, weeping and wailing as they went. Inaccessible crevices, washes, and similar spots were preferred for graves. The flexed and bound corpse was placed in a sitting position or on its side in the crevice, facing the rising sun. Bands that moved far away from mountainous and hilly country occasionally used the tree or scaffold burial common to many Plains tribes. In the scaffold burial, scaffolds were constructed of poles and the bodies were placed upon them; in tree burial, the bodies were wedged into the crotches of trees.