Aum-Mani-Padme-Hum is a popular Tibetan mantra, composed in Sanskrit and associated with Avilokiteshvara, is of uncertain origin.¹ It is often found carved or painted on rocks, written on paper or flags, and inserted into prayer wheels.
The repetition of the four syllables is said to recreate the ebb and flow of the universe and engender an attitude of compassion appropriate to Tibetan Buddhism.
If the mantra is inscribed on or inserted within a Buddhist prayer wheel, spinning that wheel is said to have the same effect as repeating the mantra for the same number of wheel rotations. A kind of “mechanized” prayer, perhaps.
¹ The first known citation of the mantra occurs in the Karandavyuha Sutra published in the 11th Century which appears in the Chinese Buddhist canon. However, some Buddhist scholars argue that the mantra as practiced in Tibetan Buddhism was based on the Sadhanamala, a collection of sadhana published in the twelfth century. See » http://en.wikipedia.org/wiki/Om_mani_padme_hum