From the SI mass unit to multiples and submultiples: an overview

The techniques used for generating multiples and submultiples of the kilogram are reviewed, and their historical evolution is outlined. Emphasis is given to estimation of the values of the measurands, in connection with the need for prior knowledge about them. This need has deep motivation and implies the introduction of constraints on their values. The alternatives of deterministic constraints, leading to the Lagrangian multipliers method, and uncertain constraints, leading to the minimum variance estimator, are discussed, as well as the mathematical relationship between the two methods.