增壹阿含經 3.8.p9

3.8.p9

“It also means observing, ‘Some of my breaths are long, and some are short,’ when one’s breaths are long and short. They keep their body in mind, fully knowing their breaths to be long or short. They immediately discern and are fully aware of it as they breath in and out. If they keep their body in mind while knowing their breaths are long or short, then they will also know the number of breaths that are long or short, discerning and understanding it clearly.