In a mixing bowl take idli rice,urad dal and methi seeds.Soak it for 5 hours.Rinse it well atleast twice.Drain water.
Transfer to a mixer grinder and grind.Sprinkle water as and when the batter is dry.Grind it to a smooth fluffy batter like we grind for idli batter.Transfer the batter to a tall container.
Add ragi flour to it.Add required salt.
Add little water mix well to form a flowing thickish batter.
Keep covered and allow it to ferment for 8-10 hours.I left it overnight in a warm place in the kitchen.See the batter is fermented now, I forgot to click a picture of the risen batter.Mix really well.You can use this batter as such for idli and take a portion of it and dilute with water.
The dosa batter should be runny like this.
Heat dosa tawa. In medium flame add the dosa batter to the dosa tawa and keep spreading in circular motion outwards.Drizzle oil and cook for few seconds.
When the dosa gets slightly browned turn over to other side and cook for few seconds then flip over and fold it.Serve hot!