Here is a URL about medieval banquets.
http://www.fpm.wisc.edu/safety/banquet/BANQUET.htm It is earliest I have found mention of social putdown by being seated "below the salt". I have wondered about the origin of this. Salt was not expensive. There were many trade routes for salt by 500 BC. In England there were places where salt was obtained in Iron Age, and many during Roman occupation of Britain. In Domesday Book over a thousand were listed. Salt was not cheap, but it was not the cost, I suspect, but the dirty hands of lowclass guests that put them where they could not pollute the salt. Salt shakers would have been quite impractical at that time, since it would have taken a skillful craftsman to make the perforated top, and humidity would have kept it from working. I suppose rock salt could be ground to get small particle size. But fine white tablesalt did not become available until a couple hundred years ago, when it was discovered that an upwelling of brine in evaporating pan would suspent suitable sized crystals.
