Mbh 1.2.5

“Sauti said, ‘One chariot, one elephant, five foot-soldiers, and three horses form one Patti; three pattis make one Sena-mukha; three sena-mukhas are called a Gulma; three gulmas, a Gana; three ganas, a Vahini; three vahinis together are called a Pritana; three pritanas form a Chamu; three chamus, one Anikini; and an anikini taken ten times forms, as it is styled by those who know, an Akshauhini. O ye best of Brahmanas, arithmeticians have calculated that the number of chariots in an Akshauhini is twenty-one thousand eight hundred and seventy. The measure of elephants must be fixed at the same number. O ye pure, you must know that the number of foot-soldiers is one hundred and nine thousand, three hundred and fifty, the number of horse is sixty-five thousand, six hundred and ten. These, O Brahmanas, as fully explained by me, are the numbers of an Akshauhini as said by those acquainted with the principles of numbers. O best of Brahmanas, according to this calculation were composed the eighteen Akshauhinis of the Kaurava and the Pandava army. Time, whose acts are wonderful assembled them on that spot and having made the Kauravas the cause, destroyed them all. Bhishma acquainted with choice of weapons, fought for ten days. Drona protected the Kaurava Vahinis for five days. Kama the desolator of hostile armies fought for two days; and Salya for half a day. After that lasted for half a day the encounter with clubs between Duryodhana and Bhima. At the close of that day, Aswatthaman and Kripa destroyed the army of Yudishthira in the night while sleeping without suspicion of danger.