The Scripture of the Mind Seal says, “Once the returning wind mixes together, and all chaos be brought into harmony for hundred days, the work will be achieved.” In general, setting up the foundation requires a hundred days before you have real light. At this point you are still working with the light of the eyes, not the fire of spirit, not the fire of essence, not the torch of wisdom. When you have turned around the light for a hundred days, vital energy will naturally be sufficient for true yang to rise spontaneously, and there is true fire existing in water. If you carry on the practice this way, you will naturally achieve intercourse and formation of the embryo. You are then in the heaven of unknowing, and the child thus develops. If you entertain any conceptual view at all, it is immediately a misleading path.
A hundred days of setting up the foundation does not literally mean a hundred days; one day of setting up the foundation does not mean one day. One breath of setting up the foundation does not refer to respiration. The Chinese character for breath (息) is made up of the characters for Self (自) and mind (心). The Self (自) and the mind (心) sustaining it, is the true breath (息), which also refers to the primordial spirit – the original energy and vitality. Rising and descending, parting and joining, all start from the mind; being and non-being, emptiness and fullness, are all in the mind. To realize one true breath, it takes a lifetime’s work, not just a hundred days; however, a-hundred-day is one breath.
A hundred days is merely a way to indicate the importance of dedicated effort. Engaging the true breath during the day, you benefit from it at night. Engaging the true breath at night, you benefit from it during the day. A hundred days of setting up the foundation is a priceless teaching. These sayings of the realized ones all tell the truth of the human body; these sayings of the skillful teachers all speak truthfully to students. This is the mystery of mysteries, which is inexplicable; you will know it once you see your own true essence. Therefore, students must seek the teaching of a true teacher. Everything that emerges naturally from the true essence proves simply true.