The tenth part of a cent.
1791. At 20 cents pr. lb. it is 8 mills per dish.Thomas Jefferson. (N.E.D.)
1860. One hundred thousand dollars upon $400,000,000 is but one fortieth of one per cent; it is but one fourth of a mill on a dollar.Mr. Doolittle of Wisconsin, U.S. Senate, Dec. 27: Cong. Globe, p. 198/3.
1870. To begin without a mill, and to sleep the final sleep of the prosperous under a mausoleum costing a hundred thousand,that is what Wall Street did for him whom it habitually named Henry the Silent.James K. Medbery, Men and Mysteries of Wall Street, p. 153 (Boston).