
Before you start to meditate you first need to find your posture. There are 4 main postures for yogic meditation that fit all the requirements. (Virasana, Svastikasana, Siddhasana & Padmasana)
The first pose one should become adept with is Virasana, the Hero’s posture. It is an excellent introductory posture, which through daily practice will elongate the quadriceps and because of that the other meditation postures can be mastered quite easily.
It is good to start using some height so you don’t feel any pain in your knees, and as your thighs warm up & stretch you can slowly decrease the height until you gradually reach the floor. Do not rush this process; but once you can sit comfortably to the floor make sure to switch to a different posture & you can use Virasana to alternate as your resting/counter posture.

A few important points to consider is that: First, the thighs must remain parallel and not turned out. Secondly, the feet have to point straight back and not to the sides, otherwise your knees will take a huge toll. Finally, maintain the forward tilt of the pelvis as much as possible to avoid slouching.
*Ask an experienced asana instructor to safely place you in Virasana or any other meditation posture & their variations.
Virasana is far superior to sitting in a chair, even if you have to prop yourself really high. The soles of the feet are turned upward and there is a natural upward flow of prana, whereas when sitting in a chair gravitation will always pull prana down.
Requirements for meditation postures: (Use of extracts from the book Yoga Meditation – Gregor Maehle pg. 24) But what if you can’t sit in Virasana for a long time even with padding or you would like to prolong your mediation & pranayama sessions but there is still a lot of discomfort? The answer to that is Seiza or Seiza with a Meditation Bench. Sitting on your meditation bench in seiza during your daily life will greatly decrease the time needed to master Virasana and it can even be used later on as a counter posture if you are sitting for prolonged time in meditation postures like Padmasana to alleviate any knee discomfort. If you are interested in creating your own Meditation Bench check the related article here. Namaste