Wash and soak Mentya, Urid dal and Rice, in water for about 3 hours. Remove water and grind the mix to a thick batter. Mix Rice flour and Maida together and mix it to the batter, little by little. Mix Salt and keep the thick batter overnight with lid closed. Next day, add Soda and Water, bring the batter to the required consistency and bake Dosas over Tava on a moderate flame. Serve the Delicious Dosas with Coconut chutney.