Legend of the Ambalappuzhaa Paal Paayasam
According to the legend, Lord Krishna once appeared in the form of a sage in the court of the king who ruled the region and challenged him for a game of chess (or Chaturanga). The king being a chess enthusiast himself gladly accepted the invitation. The prize had to be decided before the game and the king asked the sage to choose his prize in case he wins. The sage told the king that he had a very modest claim and being a man of few material needs, all he wished was a few grains of rice. The amount of rice itself shall be determined using the chess-board in the following manner. One grain of rice shall be placed in the first square, two grains in the second square, four in the third square, eight in the fourth square and so on. Every square will have double the number of grains of its predecessor.
Upon hearing the demand, the king was unhappy since the sage requested only a few grains of rice instead of other riches from the kingdom which the king would've been happy to donate. He requested the sage to add other items to his prize but the sage declined.
So the game of chess started and needless to say the king lost the game. It was time to pay the sage his agreed-upon prize. As he started adding grains of rice to the chess board, the king soon realised the true nature of the sage's demands. By the 20th square, the number had reached one-million grains of rice and by the 40th square, it became one-trillion. The royal granary soon ran out of grains of rice.
- The king realised that even if he provides all the rice in his kingdom and his adjacent kingdoms, he will never be able to fulfill the promised reward. The number of grains was increasing as a geometric progression and the total amount of rice required to fill a 64-squared chess board is (2^ (64) - 1 ), which is equal to 18446744073709551615 grains (about 18*10^18, or 18 billion billion grains). This amount of rice would weigh about 460*10^12 kg, 4.6*10^2 Pg (Peta grams), or 460 billion tonnes (1,000 grains of rice weigh about 25g). This amount of rice would also cover the surface of India two meters deep!
Upon seeing the dilemma, the sage appeared to the king in his true-form, that of lord Krishna. He told the king that he doesn't have to pay the debt immediately but can pay him over time. The king shall serve Paalpaayasam (made of rice) in the temple freely to the pilgrims every day until the debt is paid off.
And so it continues to this day.