James Clerk Maxwell on quantities and units

In the scientific literature the equation $Q=\{Q\}[Q]$ is frequently quoted, where $Q$ denotes a quantity, $\{Q\}$ a numerical value, and $[Q]$ a unit. During the last years some experts claimed, that this equation is due to James Clerk Maxwell. This is obvious, they say, from the opening sentences at the beginning of Maxwell's book "A Treatise on Electricity and Magnetism". In this paper it will be shown that this view cannot be justified.