The NIST blog has a very nice and readable post about #standards for metrics and the history of how the same metrics developed from being based on physical objects and distances to universal constants.
www.nist.gov/blogs/taking...
nist.gov
5 Weirdly Nonstandard Things About the Metric System
The modern metric system — known as the International System of Units, or SI — is a model of consistency and logic. Or is it?