_Swearing by Swans._--
"At the banquet held on this occasion, he vowed before God and the
_swans_, which according to usage were placed on the table, to punish
the Scottish rebels."--Keightley's _History of England_, vol. i. p.
249. ed. 1839.
What authority is there for this statement respecting the swans? What was
the origin and significance of the usage to which allusion is here made?