What is the appropriate lentil-to-water ratio for stovetop lentils?
In surveying the web, I have found a variety of ratios from 1:2 to 1:4 by volume, and some which measure the toor dal by weight.  

I suspect some of the variation comes from the desired outcome (more or less soupy or poridgy), and whether or not the peas were pre-soaked.

You can google "toor dal recipe without pressure cooker".

This recipe for stove top toor dal suggests pre-soaking, and then using a 1:2 ratio of water.  The author provides lots of pictures and explanation.