“Having seated [himself] in … a room and free from all anxieties, [the student] should practice Yoga, as instructed by his guru.” [Hatha Yoga Pradipika I-14]
Straightforward advice. What type of room you may wonder? Well the room is easy to come by. Simply find yourself
“… a small room of four cubits square, free from stones, fire, water and disturbances of all kinds, and in a country where justice is properly administrated, where good people live and food can be obtained easily and plentifully… The room should have a small door, be free from holes, hollows, neither too high nor too low, well plastered with cow-dung and free from dirt, filth and insects.” [HYP I-12&13]
Well, finding a place like this can’t be too difficult, can it? Cow dung is plentiful and probably available at your local Safeway. Justice is universal today. That is all easy … but what the heck is a cubit? 
The above teaching shows us that advice given in ages past may not be the best advice for us in our current age. Having a good teacher who can interpret the teachings and intentions of the gurus of the ages and bring the teachings to us in a modern manner is invaluable. 
The Three Tattvas of Yin Yoga Practice
A tattva is the reality of a thing, or its category or principal nature. Sarah Powers offers us three very simple and very effective principles for the yin practice.
- Come into the pose to an appropriate depth
- Resolve to remain still
- Hold the pose for time
Remembering these three principles as you practice will simplify everything. We will look at each step of how to practice in more detail in a moment. Knowing when to practice is a different matter.
- — Actually, a cubit was considered to be the length of a man’s arm, from the elbow to the tip of the fingers, or about eighteen inches. So this would mean you need only about six feet of space (assuming you are not more than six feet tall)
- — For my own part, I am indebted to Sarah Powers and Paul Grilley, who have guided me and so many others in our learning of Yin Yoga. When I open my mouth to teach or sit down to type this book, it is their voices that come out.