Quintilian on Memory
From what Simonides did on that occasion, it appears to have been remarked that the memory is assisted by localities impressed on the mind, and everyone seems able to attest the truth of the observation from his own experience, for when we return to places, after an absence of some time, we not only recognize them, but recollect also what we did in them. Persons whom we saw there, and sometimes even thoughts that passed within our minds, recur to our memory. Hence, in this case, as in many others, art has had its origin in experiment. People fix in their minds places of the greatest possible extent, diversified by considerable variety, such as a large house, for example, divided into many apartments. Whatever is remarkable in it is carefully impressed on the mind, so that the thought may run over every part of it without hesitation or delay. Indeed, it is of the first importance to be at no loss in recurring to any part, for ideas which are meant to excite other ideas ought to be in the highest degree certain. They then distinguish what they have written, or treasured in their mind, by some symbol by which they may be reminded of it, a symbol which may either have reference to the subject in general, as navigation or warfare, or to some particular word, for if they forget, they may, by a hint from a single word, find their recollection revived. It may be a symbol, however, of navigation, as an anchor, or of war, as some particular weapon. These symbols they then dispose in the following manner: they place, as it were, their first thought under its symbol, in the vestibule, and the second in the hall, and then proceed round the courts, locating thoughts in due order, not only in chambers and porticoes, but on statues and other like objects. This being done, when the memory is to be tried, they begin to pass in review all these places from the commencement, demanding from each what they have confided to it, according as they are reminded by the symbol. Thus, however numerous are the particulars which they have to remember, they can, as they are connected each to each like a company of dancers hand to hand, make no mistake in joining the following to the preceding, if they only take due trouble to fix the whole in their minds. What I have specified as being done with regard to a dwelling house may also be done with regard to public buildings, or a long road, or the walls of a city, or pictures, or we may even conceive imaginary places for ourselves.
However, we must have places, either fancied or selected, and images or symbols which we may invent at pleasure. These symbols are marks by which we distinguish the particulars which we have to get by heart, so that, as Cicero says, we use places as waxen tablets and symbols as letters. But it will be best to cite what he adds, in his exact words: “We must fancy many plain and distinct places, at moderate distances; and such symbols as are expressive, striking, and well-marked, which may present themselves to the mind and act upon it at once.” I am therefore the more surprised that Metrodorus should have made 360 places in the twelve signs through which the sun passes. This was doubtless vanity and boastfulness in a man priding himself on his memory as the result of art rather than as the gift of nature.
Quintilian then goes on to say that the technique might be useful for memorizing things in a specific order, but is not as useful for memorizing speeches word-for-word.