Salt cellars were a vessel used to store salt until the invention of the salt shaker in 1858. The salt cellar was given to the head of the table at the beginning of a meal, and subsequently passed around the table in an almost ceremonious style. Where each guest sat at the table, in relation to the salt cellar, determined his/her status.
Long form articles:
At the King’s Table: Royal Dining Through the Ages
Groom, Susanne
Published by Merrell Publishers (2013)
Disappointingly Muddy 