[thaumasiotes]

You need to move seawater into an area where it won't empty back into the sea. This requires a jar.

And you need to carry the salt. That's it. Salt can't rot and it's needed everywhere; this is just about the easiest piece of commerce you can do.

[Xylakant]

Turning seawater into salt by evaporating it works in areas where evaporation is substantially higher than precipitation, so mostly in dry, warm areas. It won’t work very well in Northern Europe for example. Salt needs to be kept moderately dry when transporting it, while it can’t rot, it’s still not trivial to transport.

And salt was not only flavoring, but one of the few means of preserving food. Access to salt was not a mere culinary issue, it was a matter of survival. This means that there was substantial trade, and substantial value in salt production and trade.

[refurb]

Turning seawater into salt by evaporating it works in areas where evaporation is substantially higher than precipitation, so mostly in dry, warm areas.

Agree Northern Europe would be tough, but there are plentiful salt ponds in Vietnam where the humidity (plus the rain) would make one think evaporation would be challenging, but apparently it works.

[Spooky23]

Very simple. Now scale it to feed an army with 2000 year old technology.

[andrewflnr]

Ok, but remember, in this benighted subthread, we're comparing with a proposal to move seawater instead, in equivalent amounts.

[thaumasiotes]

I can't tell what you think you're saying. Not only was this done routinely, it was much easier than the more obvious problem of providing the army with grain.