Algorizmi said:
since I had seen that the Indians had set up IX symbols in their universal system of numbering, on account of the arrangement which they established, I wished to reveal, concerning the work that is done by means of them, something which might be easier for learners if God so willed. If, moreover, the Indians had this desire and their intention with these IX symbols was the reason which was apparent to me, God directed me to this. If, on the other hand, for some reason other than that which I have expounded, they did this by means of this which I have expounded, the same reason will most certainly and without any doubt be able to be found. And this will easily be clear to those who examine and learn.
So they made IX symbols, whose forms are these: (9 8 7 6 5 4 3 2 1). ...
And I have found that the Indians worked according to these places. Of these, the first is the place of the units, in which is doubled and tripled whatever is between one and IX. The second is the place of the tens, in which is doubled or tripled whatever is from X to ninety. The third is the place of the hundreds, in which is doubled and tripled whatever is from C to DCCCC. But when X was put in the place of one and was made in the second place, and its form was the form of one, they needed a form for the tens because of the fact that it was similar to the form of one, so that they might know by means of it that it was X. So they put one space in front of it and put in it a little circle like the letter o, so that by means of this they might know that the place of the units was empty and that no number was in it except the little circle, which we have said occupied it, ...