The Collaborative International Dictionary of English v.0.48:

Corsned \Cors"ned\ (k[^o]rs"n[e^]d), n. [AS. corsn[=ae]d.] (AS.
   Laws)
   The morsel of execration; a species of ordeal consisting in
   the eating of a piece of bread consecrated by imprecation. If
   the suspected person ate it freely, he was pronounced
   innocent; but if it stuck in his throat, it was considered as
   a proof of his guilt. --Burril.
   [1913 Webster] cortege

Bouvier's Law Dictionary, Revised 6th Ed (1856):

CORSNED, ancient Eng. law. This was a piece of accursed bread, which a
person accused of a crime swallowed to test his innocence. It was supposed
that, if he was guilty, it would choke him.