Some Buddhist sects use the Prayer Wheel. It's often described as a physical means of sending a supplicant's prayers to Heaven, but I understand that's an over-simplification of the beliefs.
The picture above shows a hand-held Tibetan Prayer Wheel (which I actually purchased in Toronto during my visit in 2004 described here). The metal drum houses prayers inscribed on a coil of paper.
A weight attached to a chain assists the supplicant in rotating the drum continuously, always in a clockwise direction, by repeated movement of the wrist.
In Tibet, I've seen larger versions of the hand held prayer wheel, where the supplicant wears a leather shoulder strap with a pouch at the bottom to locate the end of the wooden handle, rather like a Standard Bearer might use.
Perambulating clockwise around the outside of the Jokhang Temple in Lhasa, the Tibetan gentleman in the foreground has a larger prayer wheel.
Sometimes, the rotating drum of the Prayer Wheel is mounted in a fixed supporting frame, and examples may be found singly or in groups.
A group of six Prayer Wheels on the way to the Tiger's Nest Monastery, Bhutan.
A large group of Prayer Wheels, Cheri Goemba, Bhutan.
Prayer Wheels on temple steps, Miyajima, Japan.
Roadside Prayer Wheels on Lhasa - Shigatse Road, Tibet.
Roadside Prayer Wheels, Nangartse, Tibet.
Once the rotating drum of the Prayer Wheel is mounted in a fixed supporting frame, the drum can become much larger, turned by handles or ropes attached to the drum.
A LARGE Prayer Wheel in the town of Whangdue Phodrang, Bhutan.
The Water Powered Prayer Wheel
In Tibet and Bhutan there are water-powered Prayer Wheels, where a stream is arranged to turn a wooden paddle wheel. The rotating drum often carries an arm which strikes a small bell on each revolution, producing a tinkling sound.
A Water-Powered Prayer Wheel, Bhutan.
The Solar Powered Prayer Wheel
I think I first saw the solar powered prayer wheel in Mongolia (described in the post Leaving Ulaan Baatar - The Reality). Deposited on a cairn of stones (called an 'Ovoo') was a miniature prayer wheel happily spinning on its own, electrically-driven from a small photo-voltaic panel in the base. Later, I saw the same thing mounted on the dashboard of cars. I was intrigued by the conjunction of ancient belief and modern technology. My visit to Tibet in 2013 described here finally gave me the opportunity to purchase an example. The shop in Lhasa had dozens of different sizes, colours and decorative styles on offer. The very inexpensive models were not solar powered but required a battery to spin the miniature prayer wheel.
A solar-powered Prayer Wheel.
Other types of Prayer Wheel
I've only spotted one butter lamp powered Prayer Wheel. This was at the Drepung Monastery in Lhasa. A small butter lamp is placed under a glass case and the rising warm air turns a fan attached to a lightweight prayer wheel suspended above.
Butter lamp powered Prayer Wheel, Drepung Monastery, Lhasa, Tibet.
I believe there are wind powered Prayer Wheels but I've not spotted one, I'm afraid.
My pictures
The Prayer Wheel