(Ibid. 14) "There shall not be unto you in your house a measure and a measure": I might think that one should not make a measure of a kav, a tarkav, a half-tarkav, and a quarter tarkav; it is, therefore, written "great and small" — a great which "falsifies" the small, i.e., he should not take (merchandise) with the great and return with the small, (giving the impression that he is using the same measure).
R. Akiva says: Whence is it derived that one should not keep an imperfect measure for use in his own home? From "There shall not be unto you in your house."