Harness cask : A tub lashed to a vessel's deck and containing salted provisions for daily use; -- called also harness tub.

Example:


Taxonomy
Fact Monster, Harness, large cask, Dictionary of Phrase and Fable, Reference Desk, tub, rim, salt, meat, Nautical term, E. Cobham Brewer, King James version, translation, J. M. Rodwell, Charles and Mary Lamb, Family Education Network, Quizzes, Twilight.

Defination from the web:
... Harness Cask. A large cask or tub with a rim cover, containing a supply of salt, meat for immediate use. Nautical term. ...