Khan Academy: Prayer Wheel

Prayer wheels are an example of Buddhist technology. This technology allowed the faithful to multiply the number of prayers they expressed by millions. This is because prayer wheels are filled with copies of mantras (sacred spells associated with particular deities) such as the mantra of Avalokiteshvara, "om mani padme hum." The mantra is printed on very thin tissue paper as many times as possible, in some cases numbering in the millions. The paper is wrapped around a spindle and covered with a protective cylinder. In recent years, microfilm technology has allowed billions even trillions of prayers to be invoked with just one turn of the wheel.