7 CFR 29.1109: Rule 3.

In drawing an official sample from a hogshead or other package of tobacco, three or more breaks shall be made at such points and in such manner as the inspector or sampler may find necessary to determine the kinds of tobacco and the percentage of each kind contained in the lot. All breaks shall be made so that the tobacco contained in the center of the package is visible to the sampler, except for baled tobacco that is not opened for inspection (see Rule 30). Tobacco shall be drawn from at least three breaks from which a representative sample shall be selected. The sample shall include tobacco of each different group, quality, color, length, and kind found in the lot in proportion to the quantities of each contained in the lot.