ABSTRACT
And if thou makest a mistake in the foundation of the year of the Arabs, or if thou dost not know which it is, add of the years of Alexander nine hundred and fourteen, and what remaineth over with thee cast out, seven by seven (?), that is to say, from thirty take two, from one hundred take two(?), and from two hundred take four, and from four hundred take eight, and from eight hundred take sixteen, and from one
Fol. 2t5b. thousand take twenty. And when thou hast cast out I those years of Alexander which are in excess of nine hundred and fourteen seven by seven, see how many remain with thee. If seven remain, that number is the foundation. If the total is more than seven, strike out seven. Then what remaineth in thy hand double four times, and see what their total is. Then reject seven by seven and see how many remain with thee. If the remainder be one, then one is the foundation, and if two, two is the foundation, and if three, three is the foundation, and if four, four is the foundation, and if five, five is the foundation, and if six, six is the foundation, and if seven, seven . is the foundation.
