A constant difficulty in studying works on metrology is the need of distinguishing the absolute facts of the case from the web of theory into which each writer has woven them -- often the names used, and sometimes the very existence of the units in question, being entirely an assumption of the writer.
And coins have long been recognized as one of the great sources of metrology -- valuable for their wide and detailed range of information, though most unsatisfactory on account of the constant temptation to diminish their weight, a weakness which seldom allows us to reckon them as of the full standard.
Buildings will generally yield up their builder's foot or cubit when examined (Inductive Metrology, p. 9).
As the technology is developed, new metrology, or measurement, tools are also required.
He was also much interested in ancient weights and measures, and in 1875 published a work on Inductive Metrology.