You probably know the great Iranian (or Lebanese) mathematician and scientist Sheikh Bahai, his "The Essentials of Arithmetic", written in Arabic, was translated several times into other languages and was a standard textbook until the beginning of the 20th century.
Sheikh Bahai built a wonderful bath in Isfahan, the fact that this bathhouse was kept warm with just a candle for centuries was a big mystery for scientist for many years.
In the past, people didn't have private baths in their houses; instead, there were public bathhouses, which were places with big pools of warm water, which people sat around in. The Sheikh Bahai bath was one of those public baths, which could accommodate hundreds of people at the same time and which was kept warm by just a candle.
Around the early 19th century, a group of British scientists became curious about the Sheikh Bahai bath and decided to discover its secret. They dismantled the area where the candle had been placed in the wall, but they could not find anything and their effort failed. They tried to fix it but the candle never worked again as before. Later, other scientists said that it must have been some kind of nuclear fuel from deep under ground that kept the candle going and was some how sealed by the British destroyers.