修習止觀坐禪法要 1.78

1.78

二、住坐中調三事者，行人當於一坐之時，隨時長短，十二時、或經一時，或至二三時，攝念用心，是中應須善識身息心三事調不調相。若坐時向雖調身竟，其身或寬或急，或偏或曲，或低或昂，身不端直，覺已隨正，令其安隱；中無寬急，平直正住。

Second, harmonizing the three things while dwelling in sitting: during a single sitting, according to the length of time—throughout the twelve two-hour periods, or for one period, or up to two or three periods—the practitioner collects mindfulness and directs the mind; therein one must skillfully recognize the harmonized and unharmonized characteristics of the three things: body, breath, and mind. When sitting, although one previously finished harmonizing the body, the body may become either lax or tense, tilted or crooked, lowered or raised, not upright and straight; upon noticing this, one should immediately correct it, making it secure and comfortable, centered with neither laxity nor tension, sitting level, upright, and straight.