Eliae Vineti ... de logistica libri tres

...hundred and ninety, and seven thousand and nine hundred, and eight thousand and nine hundred: whose sum is one hundred and fifteen thousand, two hundred and ten. Those digits which are in the first position, together with many circles, make only 10. Because this number ten is of two signs, the first of them, 0, is to be marked under the line in the very perpendicular of the first position; the other is to be reserved for the second position. That position, since it has nothing other than circles, would have a single one marked under the line for so many, if something had not been reserved from the preceding position. But a unit was reserved, which is to be marked under instead of those circles. Now the third position exhibits 9 twelve times and 4 once, which make one hundred and twelve. Of this number, which is marked thus, 112, the first sign 2 ought to be placed under the line in that same third position, and the rest reserved for the following positions.

23

slower memory?

• But indeed, so that a slower memory does not deceive anyone, it will be safest to draw another straight line beneath the sum and to place under that line the numbers that have emerged a little larger from the composition of several digits, having diligently related their individual signs to the positions to which they pertain. As here, beneath the sum, you see the first sign of those one hundred and twelve, 2, written to the third [position], and the following unit to the fourth, and the other unit...