‘You should not be tilted sideways, backwards or forwards. You should be sitting straight up as if you were supporting the sky with your head. This is not just form or breathing. It expresses the key point of Buddhism. It is a perfect expression of your Buddha nature. If you want true understanding of Buddhism, you should practice this way. These forms are not a means of obtaining the right state of mind. To take this posture itself is the purpose of our practice. When you have this posture, you have the right state of mind, so there is no need to try to attain some special state. When you try to attain something, your mind starts to wander about somewhere else. When you do not try to attain anything, you have your own body and mind right here’.
I have often used this paragraph when teaching workshops. I find it interesting that this is in the first chapter of Zen Mind, Beginner’s Mind, and I feel like it expresses the very root of what we do, clearly and simply.