There was a king in ancient India, so the story goes, who was very fond of intellectual discussions and used to invite scholars from far and near to his court room. He used to love the discussions that followed in a variety of topics and was well known for his genorosity in rewarding those participating scholars.
One time he was so impressed by a visiting scholar for his remarkable skill in the game of chess that he asked him to choose his gift and assured him that it will be granted whatever it may be. The scholar inspite of polite refusal was forced to express his wish.
He then said "Your Excellency here is my wish, in the chess board there are 64 squares, I want you to give me one rice grain for the first square two for the second four for the third eight for the fourth and so on till you reach the last square. For each square you should give me double the rice grains that the previous sqaure represents."
The King was taken a back at such a "silly" request. He implored the scholar to ask for something more substantial, the scholar struck to his request. The king ordered his ministers to fulfill the scholar's request. Soon he found out that it is impossible to fulfill the demand.