摩訶止觀 2.115

2.115

又約一種三昧亦具四悉檀意。若樂行即行，樂坐即坐。行時若善根開發入諸法門，是時應行；若坐時心地清涼喜悅安快，是時應坐。若坐時沈昏，則抖擻應行；行時散動疲困，是則應坐。若行時怳焉虛寂，是則應行；若坐時湛然明利，是時應坐。餘三例爾（云云）。

Furthermore, even a single kind of samādhi contains the sense of the four siddhāntas. If one delights in walking, one walks; if one delights in sitting, one sits. When walking, if wholesome roots unfold and one enters dharma gates, at that time one should walk. When sitting, if the mind-ground is cool, refreshing, joyful, and tranquil, at that time one should sit. If while sitting one sinks into torpor, one should shake it off and walk; if while walking one becomes distracted and fatigued, one should sit. If while walking one is suddenly vacant, calm, and serene, one should walk; if while sitting one is clear, lucid, and keen, at that time one should sit. The remaining three are analogously understood (and so on).