I love Hindu squats, and I do them every week.
They have been practiced in India by wrestlers for thousands of years, they develop your quads, your feet, and ankles. They strengthen your knees, they build phenomenal strength endurance, and cardiovascular conditioning as well.
They are typically paired with Hindu push-ups, for every one push-up you do two squats.
these are not done super slow, they are meant to be done rhythmically with bounce.
Supposedly the greatest wrestlers would do over 1000 a day.
I suggest starting with 50 to 100 and building up from there. Once you can do 200 to 300 in a workout, it depends on your training goals if you want to do more.
I have never added more than 15 kg, using a weight vest, when doing these, and only for 100 reps, which has given me a level of quad development, I am happy with.