So I found all the orange levers, and a small cutscene happened about a chest appearing out of nowhere in the middle of nowhere. There's not a single landmark in that brief scene so I have no idea where to look. Does anyone know?
Nevermind, I found it. The chest appears on the adjacent side of land from the fortune teller. In fact, right between her and the cave where you find the Crystal Skull and the three lesser creatures.