What is the spiritual symbolic meaning of hand size?

In the Tamil literature there is an old saying: "கற்றது கை மண் அளவு கல்லாதது உலகளவு என்பது விவேகம்." It means all knowledge acquired in this life time is equivalent to only a fist full of sand and the knowledge not acquired in this life time is equivalent to this whole world. Here the hand size symbolizes the knowledge.