The Everest Basecamp trek will take you thru many small and big monasteries. The prayer wheel is a common sight. 'A prayer wheel is a cylindrical wheel on a spindle made from metal, wood, stone, leather or coarse cotton. Traditionally, the mantra Om Mani Padme Hum is written in Sanskrit on the outside of the wheel.
According to the Tibetan Buddhist tradition based on the lineage texts regarding prayer wheels, spinning such a wheel will have much the same meritorious effect as orally reciting the prayers' @wikipedia