Once you've reached the Proficient level in the Yucatec Dialect, you'll be able to read this monolith (1/7), which is located roughly in the middle of the southern part of the city. (Check the annotated level map if you're having trouble finding it.)
Reading the monolith reveals a clue: "Canals bring water to the arid parts of the village, and they washed me away."
Selecting the monolith on the in-game map reveals the area in which the hidden treasure can be found.
Follow the water flowing through the narrow stone troughs near the monolith.
The water flows down several ledges and around to the right (south). On the way down, jump onto the wooden platform in the roofless house below on the right. Drop down to the floor...
...and dig up another survival cache (4/34).
Climb out in the corner to the left of the wooden door slats.
Continue following the flowing water, down a few more ledges...
...eventually ending up in the muddy, open area to the south.
Search the ground at the foot of the stairs, near the little pool built into the stone wall, to find the monolith riches, a survival cache (5/34).