Standards of Weights and Measures Act, 1976
34. Any custom, usage, etc., contrary to standard weight, measure or numeration to be void. –
Any custom, usage, practice or method of whatever nature which permits a person to demand, receive, or cause to be demanded or received, any quantity of article, thing or service (to which this Part applies) in excess of, or less than, the quantity specified by weight, measure or number in the contract or other agreement in relation to the said article, thing or service, shall be void.