The study of Zen means the practice of zazen. ‘To practice zazen choose a quiet place that is neither draughty or damp, and use a thick mat. [Since we are using the same sitting posture as Shakyamuni when he received enlightenment] think of the place where you sit as the “Diamond Seat.” Some monks practice on large stones while others follow [the seven Buddhas] by practicing zazen on a mat of wild grasses.

The place for zazen should not be too dark but kept moderately bright day and night. It should be kept warm in winter and cool in summer. Keep the body and mind at rest - cut off all mental activity. Do not think about time or circumstances, nor cling to good or bad thoughts. Zazen is not self-consciousness or self-contemplation. Never try to become a Buddha. Detach yourself from notions of lying or sitting. Eat and drink moderately. Do not waste time. Pay attention to your own practice of zazen.

learn from the example of the fifth Patriarch Kōnin of Mt. Ōbai. All of his actions, everyday, were the practice of zazen.

When your practice zazen wear a kesa and use a small round cushion. Do not sit on the middle of the cushion but place the front part under your buttocks. Cross your legs and put them on the mat. The cushion should be touching the base of your spine. This is the basic posture that has been handed down from Buddha to Buddha, Patriarch to Patriarch.

Use either the full or half lotus posture. In the full lotus, the right foot is placed the left thigh and the left foot on the right thigh. Keep your legs horizontal, and your back perfectly straight.  In the half lotus the left foot is placed on the right thigh and the right foot is tucked underneath the left thigh.

Loosen your robe and straighten up. Right hand on left foot, left hand on right foot. The thumbs should be straight and touching lightly. Both hands should be against your abdomen. The top of your thumbs should be kept even with the navel. Remember to keep your back straight at all times. Do not lean to the right no left, or front or back. Keep your ears even with your shoulder. Likewise the nose and the navel should be in the same plane. Place the tongue against the roof of your mouth. Breath through your nose and keep your teeth and lips together. The eyes should be kept open in their natural way. When you begin, adjust your body and mind by taking a deep breath. 

The form of your zazen should be stable like a mountain. Think “not-thinking.” How? By using “non-thinking.”

This is the splendid way of zazen. Zazen is not the means to enlightenment, zazen itself is the completed action of the Buddha. Zazen itself is pure, natural enlightenment.

This was delivered to the monks of Kippōji in November of 1243

Shōbōgenzō (The Eye and Treasury of the True Law) by Dōgen Zenji, tr. Kōsen Nishiyama and John Stevens, pub. Nakayama Shobo Japan.