The literary debut of the Prince of Sansevero coincided with the publication, in 1747, of the Easiest and most useful Practice of Military Exercises for the Infantry, printed by the typographer Giovanni di Simone and dedicated to King Charles. The work was enormously successful and confirmed the fame of Raimondo di Sangro throughout Europe. His exceptional knowledge of the matter won him praise from Louis XV of France, from the Marshal of Saxony and, especially, from Federico II of Prussia, whose military organisation the Prince looked to as a model. The Spanish army adopted the Prince’s useful exercises, which he had already tested on the field with his Capitanata Regiment.
After publishing the Lettera Apologetica, his inclusion in the Index and severe attacks by various writers led Raimondo di Sangro to write a Supplication to Pope Benedict XIV (Naples 1753), in the vain attempt to have the Lettera removed from the list of forbidden books. Demonstrating his vast culture and mordant dialectic skills, in his Supplication, the Prince destroys all the objections of his censors regarding the delicate subjects he deals with in the Apologetica. Above all, the author answers the insinuation whereby his writings may have communicated, using an “evil jargon” (i.e. in code) esoteric contents and principles contrary to the doctrine of the Church. The only “innocent jargon” which di Sangro admits to using is irony.
In 1753, di Sangro published in French the Lettres écrites à Mons.r l’Abbé Nollet de l’Académie des Sciences à Paris, contenant la rélation d’une découverte qu’il a faite par le moyen de quelques expériences chimiques et l’explication physique de ses circonstances. Together with the Apologetica, it is the most mysterious and fascinating of the Prince of Sansevero’s works. The subject of these letters to Jean-Antoine Nollet, in fact, is the “glorious discovery” of a perpetual flame, which di Sangro made at the end of the previous year, and which he had communicated in similar letters in Italian to Giovanni Giraldi, member of the Accademia della Crusca. The discovery consisted in a substance which, once lit, had continued to burn for more than three months without undergoing the minimum “diminution”, i.e. without any reduction in weight. Despite Raimondo di Sangro’s light – like many of his fabulous discoveries – having a strong symbolic meaning and alluding intentionally to esoteric meanings, it should be underlined that in the letters to Giraldi and Nollet he illustrated procedures in line with the experimental methods of science at that time. References are made to respectable physicists, and widely accepted theoretical models of the day.
He returned to this subjects in the Dissertation sur une lampe antique trouvée à Munich en l’année 1753 (Naples 1756), also addressed to Nollet. The occasion was the discovery in Monaco of a presumably “marvellous lamp”, which was supposed to have been found still alight by those who had uncovered it during restoration work to the foundations of a church. The Prince, who analysed the lamp and the substance it contained, held it to be simply a type of phosphorus, and – half joking – postulated that it might be one of the twelve artificial phosphoruses kept in twelve carafes by rabbis from different cities around the world, symbolising the “hidden fire” which God had given to the people of Israel. In any case, di Sangro concludes that the “lamp” in Munich was not at all a light similar to the one he had discovered, and that only his light – which furthermore produced an actual flame and not a simple luminescence – could “truly be called perpetual”.
After the Dissertation, Raimondo di Sangro, motivated by a “great desire” to “keep silence” and presumably worried about running into new censure, published nothing more. However, his biographer Giangiuseppe Origlia and the Lettera Apologetica mention various works by the Prince that are still unpublished, some of which dealt with rather “dangerous” topics. Among the various texts we can mention are a Series of letters addressed to a free thinker on the moral state of atheists, the Critical dialogues on the life of Mohamed, the Dissertation on the true origin of light. He published a short extract within the Supplication concerning a Dissertation on the errors of Baruch Spinoza.
In addition to the published and unpublished titles, there are works not written by him but printed clandestinely on the press of Palazzo Sansevero. In 1751, giving a false printing address and publisher’s (“London, by Pickard”), di Sangro published Count of Gabalis or Thoughts on the secret sciences translated from French by an Italian Lady, to which is added in appendix the Rape of the Lock, poem by Mr Alexander Pope translated from the English by Signor Antonio Conti. Written and first published in Paris in 1670 by Nicolas de Montfaucon de Villars, the Count of Gabalis was considered a classic of seventeenth-century esoteric literature and Rosicrucian thought, and as such was condemned by the Church. The Italian edition too, published by di Sangro, was placed on the Index of prohibited books, together with the Lettera Apologetica. Little before the forced termination of his activity as a printer, in the end, the Prince of Sansevero just managed to publish, also with false typographical details, an Adeisidaemon sive Titus Livius a superstitione vindicatus by the Radical Enlightenment thinker John Toland, followed by Origines Judaicae by the same author.