大唐西域記 2.6

2.6

夫數量之稱，謂踰繕那（舊曰由旬。又曰踰闍那，又曰由延，皆訛略也）。踰繕那者，自古聖王一日軍行也。舊傳一踰繕那四十里矣；印度國俗乃三十里；聖教所載唯十六里。窮微之數，分一踰繕那為八拘盧舍。拘盧舍者，謂大牛鳴聲所極聞，稱拘盧舍。分一拘盧舍為五百弓，分一弓為四肘，分一肘為二十四指，分一指節為七宿麥，乃至蝨、蟣、隙塵、牛毛、羊毛兔毫、金、水，次第七分，以至細塵，細塵七分，為極細塵。極細塵者，不可復析，析即歸空，故曰極微也。

To give a brief account of matters. In point of measurements, there is first of all the yôjana (yu-shen-na); this from the time of the holy kings of old has been regarded as a day's march for an army. The old accounts say it is equal to 40 li; according to the common reckoning in India it is 30 li, but in the sacred books (of Buddha) the yojana is only 16 li.
In the subdivision of distances, a yôjana is equal to eight krôśas (keu-lu-she); a krôśa is the distance that the lowing of a cow can be heard; a krôśa is divided into 500 bows (dhanus); a bow is divided into four cubits (hastas); a cubit is divided into 24 fingers (angulis); a finger is divided into seven barleycorns (yavas); and so on to a louse (yûkâ), a nit (likshâ), a dust grain, a cow's hair, a sheep's hair, a hare's down, copper-water, and so on for seven divisions, till we come to a small grain of dust; this is divided sevenfold till we come to an excessively small grain of dust (anu); this cannot be divided further without arriving at nothingness, and so it is called the infinitely small (paramdnu).