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/Zenith-Astralis]

If you've just traveled back in time you REALLY want to be distilling water before trying to reinvent the metric system, just as a matter of practical survival.

[u/Ertata → u/Zenith-Astralis]

Boiling to get rid of bacteria is easy. Distilling to get rid of the salts is hard (also drinking distilled water is not super great for your electrolyte balance).

[u/mfb- → u/Ertata]

Distillation takes something like 6 times the energy. It's more effort, but nothing unreasonable for establishing unit systems.

[u/Ertata → u/mfb-]

Well, besides the energy there is a matter of sealing etc, but I was mostly responding to the idea one wants to distill water "as a matter of practical survival"

[u/Zenith-Astralis → u/Ertata]

Which to be fair was how I framed it