坐禪三昧經 1.60

1.60

問曰：「入出息是一息。何以故？出息還更入故。譬如含水水暖，吐水水冷，冷者還暖，暖者還冷故。」

Question: "The inhalation and exhalation are one single breath. Why is this? Because the exhalation goes back in again. For example, if water is held in the mouth, the water becomes warm; if one spits out the water, the water becomes cool; because the cool becomes warm again, and the warm becomes cool again."