The mnemonic snake in “Secretum de Thesauro” (Giovanni Fontana, 1430 ca)
“Secretum de thesauro experimentorum ymaginationis hominum” (secret of the treasure of experiments in man’s imagination, BNF NAL 635) is a cipher manuscript by the Venetian Giovanni Fontana dating to 1430 ca. A large part of the booklet is devoted to the description of mnemonic devices and mnemonic techniques related with the subjects discussed by Frances Yates in her classical essay “The Art of Memory” (1966).
A particularly complex device is described and illustrated at f29v-31r.
Transcription (by Battisti and Battisti): [29v] Simile quaxi artingenium fere videbitur, si super linea zirativam in matre signatam, posuerimus rem corpoream modice spissitudinis, et inter concavum et convexum remaneat vacuum angustum. Oportet ulterius multas dentatas rotulas in ventre illius serpentei corporis propinquas valde posuisse, que ad libitum possint circunduci. [30r] Abscondantur taliter, quod non nixi unus denticulus cerni distinte possit extra convexum corporis zirativi. Et contineat omnis rotula alfabetum in sui denticulis. Item cuiuslibet rote axis, per superiorem superfitiem serpentei corporis, mediam inter concavum et convexum, ex quodam egrediatur [30v] foramine notabiliter, sic quod manu capi possit, cum rotulas volvere voluerimus. Et quando velis experiri, volve sperula[s] inveniendo literas tibi necessarias ut supra. Et aparebunt denticuli spine serpentis in dorso; ac opus totu[m] serpens vocavi propter similitudinem.
Translation: [29v] The device will look almost like an animal if, upon the turning points marked in the inner part, we place a thin solid shell, leaving some space between the concave and convex halves. It will also be necessary to place several small gear wheels close to each other inside the belly of the snake; it will be possible to turn them at will. [30r] The wheels will be hidden in such a way that each one only shows a single tooth out of the convex body. Each small wheel will contain the whole alphabet upon its teeth. Also, the axis of each wheel should protrude [30v] from a hole in the upper surface of the snake’s body, so that it can be grasped with one’s hand when one wants to turn the wheel. When you want to use the tool, turn the wheels, finding the letters that you need, as said above [for the other tools]. The small teeth look like spikes on the snake’s spine. I called this whole creation “snake” for its similarity.
The smaller illustration at f30v is labelled “Rotula que in dorso serpentis latet” (the small wheel hidden in the back of the snake). The illustration at f31r is labelled “Serpens” (snake); I could not interpret the larger cipher word at the bottom of the page.
Battisti and Battisti (“Le macchine cifrate di Giovanni Fontana”, 1984) transcribe the sentence on the spine of the illustrated snake as: “scias quod ego sum serpens qui circulariter volvor ad memorandum omnia que dia[?] possunt infermare”. They also note that the inscription is only partially readable.
The intended meaning could be:
scias quod ego sum serpens qui circulariter volvor ad memorandum omnia qua diu possunt infirmare (know that I am a snake turning in circles to remember all those things that could weaken in time)
The gear wheel at page 30v illustrates the inner parts of the device that are mostly invisible in the f31r illustration. The body of the snake must be made in such a way that a single tooth is visible for each wheel. Each wheel can be turned by its axis that protrudes from a small hole. By selecting individual letters on the wheels, one can use this instrument to show a specific sentence. I could not think of a way to reastically arrange the wheels so that their teeth look like spikes on the back of the snake (as described by Fontana).
The device can seem trivial when seen through modern eyes, but one should consider that Fontana’s manuscript was written a few years before Gutenberg used movable characters to print books (1439). The alphabetic gear wheels can also be seen as ancestors of printing daisy wheels.
The series of mnemonic devices in the manuscript starts with a wheel called Speculum (mirror, f21r). This is a simpler device by which it is possible to compose a five letter word by independently turning the five alphabetical wheels.
The inclusion of a mirror and a snake in a series of mnemonic devices might suggest a symbolic value. The two objects were the standard attributes of Prudentia (prudence/wisdom) in personifications of this virtue.
The inscription in Palumba’s engraving was transcribed and translated by Herbert Grabes (The Mutable Glass, 1982) “Istantia Expendo Praeteritis Sequentia Necto” (I weigh the present and link the future with the past). This sentence actually explains the two faces that appear in Pisano’s and Della Robbia’s personifications: they represent the capability of looking into the past and into the future. Of course, knowledge of the past requires memory.
The connection between Memoria and Prudentia is stated by as authoritative a source as Cicero.
Cicero, “De Inventione”, II LIII 160: prudentia est rerum bonarum et malarum scientia; partes eius sunt memoria, intelligentia, providentia (wisdom is the knowledge of things that are good or bad or neither; its parts are memory, intelligence and foresight)
Cicero, “Ad Herennium”, III: appellatur prudentia scientia cuiusdam artificii; item appellatur prudentia rerum multarum memoria et usus conplurium negotiorum (the knowledge of an art is called wisdom; and again, a well-furnished memory, or experience in diverse matters is termed wisdom)
An overall analysis of the personifications of Prudentia can be found in Cesare Ripa’s Iconologia, a collection of allegories first published in the late XVI Century:
Woman with two faces, similar to Janus, who looks herself in a mirror with a snake wrapped around one arm. The two faces mean that prudence is true and certain knowledge, which orders what must be done and arises from the consideration of past and future things together. This virtue is so excellent that, by it, past things are remembered, present things are ordered and future things are foreseen. The man who is without it does not know how to regain what he has lost, nor to preserve what he possesses, nor to find what he seeks. Mirroring oneself means knowing oneself, since no one can regulate his actions if he does not know his own defects. When a serpent is attacked, it opposes its whole body to the blows, protecting its head with many spires; this shows that, in order to preserve virtue, which is almost our head and our perfection, we must expose all other things to the blows of luck; this is true for prudence as well. Therefore in the Sacred Scriptures it is said: ‘Estote prudentes sicut serpentes’ [be as prudent as snakes].”
