We don’t have any specific posture for “Sitting Silent”, you can sit as you like. On flat surface, on a cushion, on a mat or whatever. You can even sit on a stool or on a chair. You should sit comfortably so that you do not feel pain at your ankle or in your knees. If you feel pain while sitting, you cannot concentrate, instead your concentration will be diverted. It is like spoiling 15 minutes of your time. Only the thing is that we should not feel sleepy while sitting, neither we feel pain. We can sit comfortably anywhere for doing concentration practice. One thing we should try to do is that we sit straight up keeping spinal column at 900. Please do not bend or lean. If you are feeling tired, oppressed or sleepy, omit today. Let’s see tomorrow.
Here is no question of “Sitting” only, you can even do concentration while walking. We will be knowing about this very soon.