The principle is single-minded practice with a pure heart. One does not seek proof or verification – it will come by itself.
宗旨只要纯心行去，不求验而验自至。
Generally, beginners suffer from two problems: oblivion and distraction. There is a way to settle them, which is simply resting the mind on the breath.
大约初机病痛，昏沉散乱，二种尽之。却此有机窍，无过寄心于息，息者自心也。
In Chinese, the word breath is made up of the character for self and the character for heart/mind; so the breath is one’s own mind breathing. When the mind stirs, there is movement of energy. Energy is basically activity of the mind. Our thoughts are fitful and restless; the mind is wandering every single moment, with inhalation and exhalation responding to it like sound and echo. Every day we draw ten-thousand breaths and have equal number of random thoughts. As the self-illuminating energy leaks away, one gradually becomes like a withered tree or dead ashes.
自心为息，心一动，而即有气，气本心之化也。吾人念至速，雾顷一妄念，即一呼吸应之。故内呼吸与外呼吸，如声响之相随，一日有几万息，即有几万妄念。神明漏尽，如木稿灰死矣。
So should one have no thoughts? It is impossible to have no thoughts. Should one not breathe? It is impossible not to breathe. Nothing compares to making the affliction itself into medicine, which means to have mind and breath rest on each other.
然则欲无念乎，不能无念也，欲无息乎，不能无息也。莫若即其病而为药，则心息相依是已。
Therefore we should coordinate turning the light around with tuning the breath. This method totally involves activating the light of the ears. There is the light of the eyes and there is the light of the ears. The light of the eyes means unified light of the external sun and moon, while the light of the ears means unified essence of the internal sun and moon. Essence is stabilized and crystallized light. Essence and light have the same source but different names. So clarity of hearing and clarity of seeing are one, and both coming from the same spiritual light.
故回光兼之以调息，此法全用耳光。一是目光，一是耳光。目光者，外日月交光也，耳光者，内日月交精也。然精即光之凝定处，同出而异名也。故聪明总一灵光而已。
When you sit down, you lower the eyelids, and establish a point of reference. Now let go. But it is not absolutely let go – you are listening to the soundless sound of your breathing.
坐时用目垂帘后，定个准则便放下。然竟放下，又恐不能，即存心于听息。
You should not let your breathing be audible; keep it silent and just listen to its soundlessness. If it is audible, it means your breathing is too shallow and coarse, not refined enough. Just be patient, slow down and lighten up. The more you let go, the subtler it becomes. And the subtler it is, the quieter it becomes.
息之出入，不可使耳闻，听惟听其无声也。一有声，便粗浮而不入细，即耐心轻轻微微些，愈放愈微，愈微愈静，
Eventually, after a long time, all of a sudden this subtlety will be interrupted, true breathing manifests itself, and the mind-body is perceptible. When the mind is light, the breathing is subtle; when the mind is unified, the energy flows smoothly. When the breathing is subtle, the mind is light; when the energy is unified, the mind breathes at ease. Stabilization of the mind must be approached by cultivating breath-energy first, otherwise there is no way to tame the mind. So breath-energy is used as a tool, and the practice is called maintaining pure breath-energy.
久之，忽然微者速断，此则真息现前，而心体可识矣。盖心细则息细，心一则动气也，息细则心细，气一则动心也。定心必先之以养气者，亦以心无处入手，故缘气为之端倪，所谓纯气之守也。
You may not truly understand the meaning of movement. Movement is pulling the strings; it is another word for control. If you can move the mind by pulling, shouldn’t you also be able to bring it to rest by quietude and tranquility?
子辈不明动字, 动者以线索牵动言, 即掣字之别名也。即可以奔趋使之动, 独不可以纯静使之宁乎。
The sages who realized the interrelation of mind and breath-energy skillfully set up this method to benefit later generations. It says in the Book of the Elixir, “The hen can hatch her eggs because she always practices mentally listening.” These are the finest instructions. The way a hen gives life to an egg is through giving it warm energy; warm energy can only warm the shell, but cannot penetrate the inside. So the hen must also inwardly direct the energy with her mind. The act of listening is single-minded attention. When the mind penetrates, the energy enters; with warm energy, birth takes place.
此大圣人，视心气之交，而善立方便，以惠后人也。丹书云：“鸡能抱卵心常听”，此要诀也。盖鸡之所以能生卵者，以暖气也。暖气止能温其壳，不能入其中，则以心引气入，其听也，一心注焉，心入则气入，得暖气而生矣。
Even though the hen leaves her eggs from time to time, she is always listening, and her concentration is never interrupted. So her warm energy is also uninterrupted day and night, and thus the spirit comes alive. The birth of the spirit is resulted from the death of the mind. If you can kill the mind, your primordial spirit comes alive. To kill the mind does not mean to let it become withered, but to let it become concentrated and undivided. The Buddha says, “Gather the mind into one, and everything can be done.” If the mind runs off, tame it by means of breathing; if the breathing becomes rough, refine it with the mind. If you do this, how can the mind not be stabilized?
故母鸡虽有时出外，而常作侧耳势，其神之所注未常少间也。神之所注，未尝少间，即暖气亦昼夜无间，而神活矣。神活着，由其心之先死也。人能死心，元神活矣。死心非枯稿之谓，乃专一不二之谓也。佛云：“置心一处，无事不办。” 心易走，即以气纯之，气易粗，即以心细之，如此而焉有不定者乎。
Generally speaking, the two afflictions of oblivion and distraction require consistent daily practice in quietude; then the mind will naturally comes to complete rest. If you don’t practice sitting meditation, you tend to be distracted without knowing it. Once you become mindful of distraction, distraction itself becomes a mechanism to stop distraction. There is a great difference between unconscious oblivion and conscious oblivion. Oblivion that you are unaware of is real oblivion; oblivion that you are aware of is not complete oblivion, in which there is certain clarity. Distraction means the mind is wandering; oblivion means the spirit is unclear. Distraction is easy to cure; oblivion is hard to heal. When it comes to illness, symptoms like pain or itch can be treated with medicine, but oblivion is a symptom of paralysis, where there is no feeling. A distracted mind can be gathered into concentration, and a confused mind can be set in order, but oblivion is a state of stupidity and darkness. Distraction and confusion still have some direction, but oblivion means that the lower soul is in complete control.
大约昏沉、散乱二病，只要静功，日日无间，自有大休息处。若不静坐时，虽有散乱，亦不自知。既知散乱，即是却散乱之机也。昏沉而不知，与昏沉而知，相去奚啻千里！不知之昏沉，真昏沉也。知之昏沉，非全昏沉也，清明在是矣。散乱者,神驰也，昏沉者，神未清也，散乱易治，而昏沉难医。譬之病焉，有痛有痒者，药之可也，昏沉则麻木不仁之症也。散者可以收之，乱者可以整之，若昏沉，则蠢蠢焉，冥冥焉。散乱尚有方所，至昏沉全是魄用事也。
In distraction there is still a lingering presence of the higher soul, but oblivion is ruled by pure darkness and negativity. If you become drowsy when you practice sitting meditation, this is oblivion. Repelling oblivion is simply a matter of tuning the breath. The “breath” in this case is respiration through mouth and nose, not the true breath. Nevertheless true breath is in it. Whenever you sit, you should quiet your mind, let go of everything, and purify your energy. How to quiet the mind? It is done by focusing on breathing. Let the mind alone know you are breathing in and out; do not let the ears hear. When you can’t hear it, the breathing is fine. When the breathing is fine, the mind is clear. If you can hear it, it means the breathing is rough and the mind is cloudy. Cloudiness means oblivion. It is only natural for a cloudy mind to feel sleepy.
散乱尚有魂在，至昏沉则纯阴为主矣。静坐时欲睡去，便是昏沉。却昏沉，只在调息，息即口鼻出入之息，虽非真息，而真息之出入，亦于此寄焉。凡坐须要静心纯气，心何以静，用在息上，息之出入，惟心自知，不可使耳闻，不闻则细，细则清，闻则气粗，粗则浊，浊则昏沉而欲睡，自然之理也。
Even so, the mind should focus on breathing. It is focus without force. Just maintain a subtle looking and listening. This saying has a profound meaning. What is “looking”? It is using the light of the eyes to illuminate the inner self, with the eyes only looking inward and not outward. Not looking outward yet being alert is inward looking; it is not that there really is such a thing as looking inward. What is “listening”? It is using the vitality of the ears to listen to the inner self, with the ears listening inwardly only and not outward. Not listening outward yet being alert is inward listening; it has nothing to do with listening to inner noise.
虽然心用在息上，又善要会用，亦是不用之用，只要微微照听可耳。此句有微义，何谓照? 即眼光自照。目惟内视而不外视，不外视而惺然者，即内视也，非实有内视。何谓听?即耳光自听，耳惟内听而不外听，不外听而惺然者，即内听也，非实有内听。
Listening means listening to the soundless; looking means looking at the formless. When the eyes do not look outside and the ears do not listen outside, they are closed off and have a tendency to race around inside. Only by inward looking and inward listening can you ward off distraction from outside, and prevent oblivion in between, which is led on through inner racing. This is the internal sun and moon unifying their vitalities and lights.
听者听其无声，视者视其无形。目不外视，耳不外听，则闭而欲内驰。惟内视内听，则既不外走，又不内驰，而中不昏沉矣，此即日月交精交光也。
When you sink into oblivion and become drowsy, get up and walk around. Once the spirit has become clear, sit down again. It is best to sit in the early morning, for as long as it takes to burn an incense stick. After noontime, when there are too many things to do, it’s easy to fall into oblivion. Also, there’s no need to fix the length of time for sitting; it is only essential to set aside all entanglements and sit quietly for a while. Eventually you will attain absorption and not become oblivious or sleepy.
昏沉欲睡，即起散步，神清再坐。清晨有暇，坐一蛀香为妙。过午人事多扰，易落昏沉，然亦不必限定一蛀香，只要诸缘放下，静坐片时，久久便有入头，不落昏沉睡者。
Buddha Mind 