Once a demon known as Gayasura, did a heavy penance and sought a boon that whoever sees him should attain salvation (Moksham). Since salvation is achieved through being righteous in one's lifetime, people started obtaining it easily. To prevent immoral people from attaining salvation Lord Vishnu asked Gayasura to go beneath the earth and did so by placing his right foot on asura's head. After pushing Gayasura below the surface of earth, Lord Vishnu's foot print remained on the surface that we see even today. The footprint consists of nine different symbols including Shankam, Chakram and Gadham. These are believed to be weapons of the lord. Gayasura now pushed into earth pleaded for food. Lord Vishnu gave him a boon that every day, someone will offer him food. Whoever does so, their souls will reach heaven. The day Gayasura doesn't get food, it is believed that he will come out. Every day, one or the other from different parts of India will pray for welfare of his departed and offer food, feeding Gayasura.