Book 11
1.19
The next step is to distinguish something which has been written down or merely thought of by some particular symbol which will serve to jog the memory; this symbol may have reference to the subject as a whole, it may, for example, be drawn from navigation, warfare, etc., or it may, on the other hand, be found in some particular word. (For even in cases of forgetfulness one single word will serve to restore the memory.) However, let us suppose that the symbol is drawn from navigation, as, for instance, an anchor; or from warfare, as, for example, some weapon. These symbols are then arranged as follows.
