D.C. Code § 37-201.12
It shall be unlawful to sell, within the District of Columbia, any ice in any manner other than by weight, such weight to be ascertained at the time of delivery of such ice, and every person, or in case of a firm, copartnership, or corporation, the person in charge of its business in the District of Columbia, engaged in the sale of ice shall keep on each of his or its wagons or other vehicles used in the sale or delivery of ice, while in use, a scale suitable for weighing ice which has been tested and approved in accordance with the provisions of this subchapter. Every scale used for weighing ice in making sales in quantities of 100 pounds or less shall have graduations of 1 pound or less. Scales used for weighing ice in making sales in quantities of more than 100 pounds may have graduations of 5 pounds or less.
D.C. Code § 37-201.12