A saltcellar is an open dish used to hold salt. For the better part of western history, saltcellars were an essential and universal piece of tableware; oddly, they are now so rare as to be forgotten, replaced by a 19th-century invention, the closed saltshaker.
Saltcellars can be as simple as a small bowl, but many beautiful and elaborate saltcellars were developed. Salt was poured into the saltcellar at the start of the meal, and people would reach into it and get a "pinch of salt" -- literally as much salt as they could pick up between their thumb and forefinger, which they then spread over their food.
In medieval banquets, there were usually one or two very large saltcellars for the whole feast. The placement of the saltcellars was a kind of social border, with social inferiors seated below the salt -- further away from the head of the table than the saltcellars; therefore the term came to represent people of lesser quality, such as servants, journeymen, or apprentices.
By Victorian and Edwardian times, the trend was to have small (1-2 inch diameter) personal salt cellars at each place setting. These are now highly valued by collectors. Such smaller, personal saltcellars are more suited to an SCA feast than the large medieval-style ones.
The Steeleye Span album "Below the Salt" shows a large medieval saltcellar on its cover.
- Saltcellars - pictures of saltcellars from the 13th-16th centuries