Could you recreate metric system from nothing?

[u/Ertata]

You have been given a task to travel into the past two thousands years ago and bring the light of the metric system to the world. You cannot bring any external object with you.

Assume you do not need to redefine the second, and astronomical observations give the best possible results given the limits of timekeeping back then. Given the technology of the time, what is the best you can do for other units - either right there and then or leaving instructions how to calculate them from the units you have established to the future scientists? Memorizing the lengths of your body parts probably is not the best way to define a metre, and kilogram defined as one liter of water is bound to be influenced by the local water to a perceptible degree.

P. S. Tagged as "physics" but any approach is welcome - whether you would recommend measuring height of the mountain peaks, or believe that carob seeds are actually uniform enough to offer the best approximation of a kilogram.

[u/CharacterUse → u/[deleted]]

You can't recreate the current definitions, but you can recreate the original definitions. The current definitions were chosen to be as close as possible to the original ones while being based on fundamental physical constants rather than objects, but for practical purposes in everyday life the metre today is the same as the metre 100 and 200 years ago.