Maharshi Patanjali has averred - sthiram sukham
asanam i.e. that comfortable pose in which one can sit without any
body movement is termed as asana. According to Shivanand if one can
sit for three hours without any body movement, then one can attain
all the accomplishments and benefits of asanas. Obviously, he too
shares the Pantajali viewpoint. Though this is difficult initially
but certainly not impossible. To sit in meditational poses, one
requires adequate flexibility in all the muscles and above all a
healthy body. The important point regarding this asanas is that one
must hold the spinal chord straight which is not easy all the time.
Generally whenever we sit or whatever we do, we tend to tilt
ourselves in one particular direction. One may be tempted to ask,
why not use shavasana during meditational asanas. As during this
pose the body remains inactive and the spinal chord too remains
straight. But to meditate during shavasana is not so easy. One may
be easily induced to sleep and never meditate.