A large boulder with a dozen or more deep mortar bowls worn into it, known as a bedrock mortar, is located in Apple Tree Camp on the southwest slope of Devil's Peak, north of the Camp Pico Blanco. The holes were hollowed out over many generations by Indians who used it to grind the acorns into flour. Other mortar rocks have also been found within the Boy Scout camp at campsites 3 and 7, and slightly upstream from campsite 12, while a fourth is found on a large rock in the river, originally above the river, between campsites 3 and 4.