I drank of the jar.
Is this 'of' an old usage?
But I can't find the proof for that.
This tends to be an older usage.
It's not hard proof, but you will find a comparison of different versions of the same bible verse here of varying degrees of antiquity.
They compare a line in the book of Genesis
Many of the newer versions of the bible use the line:
This usage of of relates to the stuff that is consumed, not the container -- the "jar" I suppose symbolically represents its contents here (the context should make it clear).
The closest dictionary definition of contemporary use is:
You can find its use in literature.
Sacred hot springs making a comeback in Europe, NPR_Sunday, 2002:
The swamp of dreams, Harper's Magazine, 1993:
Warriors of Christendom, 1988:
War in high heels, 1993: