Astride A Cushion Meditation
SITTING ASTRIDE A CUSHION: For many people this way is easiest because you really need not be flexible in order to achive it. When you sit astride your cushion you will normally be quite high off of the ground. High enough not to put undue pressure on the ankles or lower legs. You will soon find out if you are too low because you will be in pain. I want to say that pain is NOT something one need endure in meditation. Of course a certain amount of discomfort is expected when you are a newcommer to it all-afterall, your body is not used to it. When you sit atop the cushion your legs and feet should point straight backward. They should at least be not too splayed out. Your ankles should not be bent so that your feet stick out to the side. The rest of the posture is the same either way you sit-cross legged or not-so let's move on to the cross legged position. Please see diagram above on how to exact the correct posture atop a cushion( zafu ).
Cross Legged Meditation
In general I would recommend the cross legged style unless you are more comfortable with the other styles mentioned on this site ( cushion or chair). You can sit in "full lotus" or "half lotus", or just with one leg resting in front of, or on top of, the other. These postures are never entirely symmetrical because of course on leg must be either in front of or on top of the other. So if you are going to do meditation practice, it's good to rotate the relative position of the legs. This sounds more complicated thatn it is, I promise!
Sitting Atop A Chair Meditation
It's Ok to use a chair for meditation-it should have a firm seat, though. It sometimes helps if the back legs are raised up a tad by say, a phone book or two. The resulting light tip will make it easier to keep an erect posture without too much strain. You should keep your feet planted firmly upon the floor-which will help your legs relax and your feet to gain stability and contact with the ground. Generally speaking,the back of the chair should not be used for support. If you are tall-you should try to find a chair that has long enough legs for your kness to be shorter than your pelvis. The rest of the posture is the same as siting cross legged or on the floor on a cushion-keep the body upright, not too far forward-not too far backward-but try and imagine your reaching your neck to the sky. that the entire sky is being held up by your head. Please look to the picture above for more assitence on how to meditate using a chair.