Hot water bottles

A worker dries ceramic hot water bottles in the sun before they are fired in a kiln in Tajimi, Gifu, Japan. The traditional ceramic bottle became popular again about 10 years ago as people rediscovered they were a great way to keep warm and required minimum use of electricity. They are popular among office workers, who use the ceramic bottles to keep their feet warm

Asahi Shimbun/Getty Images

A worker dries ceramic hot water bottles in the sun before they are fired in a kiln in Tajimi, Gifu, Japan. The traditional ceramic bottle became popular again about 10 years ago as people rediscovered they were a great way to keep warm and required minimum use of electricity. They are popular among office workers, who use the ceramic bottles to keep their feet warm