If any one should leave one son, that is an only son, and one or more natural sons, the legitimate son shall have two thirds of his father's substance, and the natural sons the remaining third. And if there be two legitimate sons, they shall have four parts and the natural sons a fifth, however many there may be. And if there be three legitimate sons, the natural sons shall have a seventh part. If there be four legitimate sons, the natural sons shall have a ninth part. If there be five legitimate sons, the natural sons shall have a twelfth part. But if there be more, they shall divide the substance of the father by this number.
Source:
L. A. Muratori, ed., Rerum Italicarum Scriptores, (Milan, 1725), Tome I, Part II, p. 26; reprinted in Roy C. Cave & Herbert H. Coulson, A Source Book for Medieval Economic History, (Milwaukee: The Bruce Publishing Co., 1936; reprint ed., New York: Biblo & Tannen, 1965), pp. 336-337.