瑜伽論記 7.54

7.54

又此勤修數息念者等者，謂從一數之未滿十來於中錯亂，應捨不數，還從一起，若時算數極串習故，乃至先於入息有能取轉者，有時知有。入息滅已，於息空位，有能取轉者，無時知無。次於出息已下，於彼出息知有知無。如是展轉相續流注乃至令心安住者，上來所辨眾多觀行展轉相續乃至令心安住。於入出息，應正隨行，應審了達者，於入出息單數複數或順或逆若無錯亂應正隨行，若有錯亂應審了達。於入出息，及二中間，若轉若還分位差別，皆善覺了者，若入出息起時名若轉，中聞已滅後復未生名為若還，如此轉還分位差別皆善覺了，如是名為算數修習。

Regarding 'Furthermore, when this practitioner who diligently cultivates the mindfulness of counting breath', etc.: this means that when counting from one and before reaching ten, if confusion arises in between, one should discard it, not count [further], and return to starting from one; if at the time, because the counting has become extremely well practiced, up to 'first having the operation of apprehending with respect to the in-breath', at the time of presence one knows it is present; after the in-breath has ceased, 'having the operation of apprehending with respect to the empty interval of breath', at the time of absence one knows it is absent; next with respect to the out-breath and below, regarding that out-breath one knows presence and knows absence; regarding 'thus sequentially and continuously flowing up to causing the mind to abide stably': the numerous contemplative practices differentiated above sequentially continue up to causing the mind to abide stably; regarding 'with respect to the in-and-out breaths, one should correctly follow along and should examine and discern clearly': with respect to the in-and-out breaths, whether counting single or double, forward or reverse, if there is no confusion one should correctly follow along, and if there is confusion one should examine and discern clearly; regarding 'with respect to the in-and-out breaths, and the interim between the two, whether proceeding or returning, one thoroughly understands all distinctions of stage': when the in-and-out breaths arise it is called 'proceeding'; when in the interim it has ceased and the next has not yet arisen, it is called 'returning'; all such distinctions of stages of proceeding and returning are thoroughly understood, and this is called the cultivation of counting.