Dear WW: remember I committed another "YART" (another despicable early board put-down) in mentioning "below the salt" and saying I think it was dirty hands , not just low income that dictated the custom, because the salt was in an open topped box. I haven't been able to learn when salt shakers became common. And I knew salt was abundantly available for preserving fish.
I found a site that said Domesday Book listed a bit over 1100 places in England where salt for sale was obtained from saline wells or deposits located in shallow mines. But table quality salt was harder to get.That being the case, the hosts ought to have had a second inexpensive salt supply for us peasants.