Weight; ponderousness. A colloquial term common to England and America.
Mr. Pickering says: "This noun is also used colloquially in America to signify the greater part or bulk of anything, in expressions of this kind: 'A part of the crop was good, but the heft of it was bad.'"
TO HEFT
In the United States this verb means to lift anything in order to feel or judge of its weight.
I remember the great hog up in Danwich, that hefted nigh twenty score.--Margaret, p. 111.