Meditation is to think something continuously day and night in Psalm of David 1 verse 2 it says :' But his delight is in the law of the Lord; and in his law doth he meditate day and night.' But this yoga stuff is self worshipping and idolizing one self. They said that yoga will help you to reach the higher being of yourself as you give your mind time and as you empty it. So if there is nothing in your mind while you are silent ... then that is worshipping devil through physical exercise. We have no meaning apart from God but it try to give you a meaning apart from God and it try to give you high self value and self esteem while emptying the mind.