From Trithemius, Chronicon Hirsaugiense: English translation
At this time there appeared in France an Italian man whose real name was Joannes but in his arrogance he liked to be called Mercurius. He had a wife and children, and also servants and maids who, just like him, wore linen and each of them carried their own iron chain around their neck, walking around of course in the costume which master Damis and Philostratus wrote that Apollonius of Thyana went around in. Mercurius boasted that he was an imitator and disciple of that philosopher of Thyana (opinion then held itself as it will (?)) and promised great and unheard of things, indeed miracles (not to say unbelievable things) for he boasted that he had completely mastered all the knowledge of the ancient Hebrews, Greeks and Latins, and scorned nearly all of them, both philosophers and theologians, for he said that they had all been unlearned compared with himself, and that none of them at all had been learned in secret things. Hence he claimed to be versed in every science in the world, to understand all mysteries and secrets of natural things, to be able to investigate the deep things in all scriptures, and to know everything which any man in the world could know. He affected great solemnity in public, living and behaving with gravity as one ripe with years, and he led an austere life of considerable indigence. He claimed that he was born for the highest things. He claimed that he was full of the divine spirit and boasted that he could do great things. He promised to transmute metals, as the alchemists all vainly and laboriously seek to do, and wished to seem to know everything, and be ignorant of almost nothing. He claimed that he could turn misfortune into fortune and fortune into misfortune, which he said should be done not by the aid of demons but by the art of natural magic which the ancient kings and wise men greatly prized. But as I heard from those who spoke with him, he was a semi-literate man and did not know the Latin language well. For some time he lived at Lyons in France, and did not live in the meanest place (?) but with Louis king of the French, who summoned doctors of medicine, and ordered them to examine him by disputing with him about science. The doctors summoned Mercurius at the royal command and conversed and disputed with him, and found him equal to everything, and were astonished that a man without the literacy to speak Latin adequately could have so deep an intelligence, particularly in medicine. Returning to the king after the examination, the doctors said that he knew more than a man could, but where he got it from, or whether a secret was hidden in him, they simply did not know.
This Mercurius gave king Louis a sword, crammed with 180 little blades (?) and made with his quite amazing intelligence, a shield with a mirror made with singular intelligence, which was supposed to contain some occult power or other. Then he promised the king that the queen would bear him a son who would and could be more fortunate than Alexander the Great and Charlemagne, even if the stars threatened the contrary. He promised he would by his art give the king a period of twenty years of life above his natural span. He made other claims which were not only marvellous but to my mind impossible except through God who alone can do all things. Whether he had anything of that kind from God I could not discover. When the king honoured him with gold, as soon as he left the castle he gave it all to the poor, keeping nothing for himself. I learned all this first by letter and then by word of mouth from two learned men, Eustachius and Narcissus, of whom the one lives in Lyons and the other in Paris. As a third witness I can name Joannes Wirdingus of Hasfurt, the mathematician of the Count Palatine, who today lives at Heidelberg with his prince Ludwig. For the sake of brevity I will now leave this man so as not to go on too long. What became of him, or where the amazing Mercurius now lives, I simply do not know.
Those who wrote the truth about Mercurius to us met Ferrandus, who in 1445 as a young man of 20, a golden knight, and a doctor of philosophy, medicine, theology and law came with eight horses from Spain to France, and reduced all the doctors of Paris to a stupor with his incredible knowledge. He was far the most learned in every aspect of scripture, composed with compliance with life and honesty of conversation, not arrogant, not conceited, not boastful, like Joannes Mercurius who we mentioned, but humble, restrained and modest and displaying all courtesy. Whenever he spoke with educated men he would say he was an unlearned boy, and unfit to have a conversation with experienced people, when in fact he spoke Latin with a wide vocabulary, learnedly and prudently on all topics. He had a wonderful and unbelievable memory, for he had committed to memory the Old and New Testaments, Nicolas de Lyra, the writings of Thomas Aquinas, Alexander of Hales, Bonaventure, Duns Scotus and many other theologians, as also the decretals and all the books of civil and canon law, and again in medicine Avicenna, Galen, Hippocrates, Aristotle, Plato, Albertus Magnus and all books of philosophy so perfectly that he did not have an equal. He was most quick at allegation, solid and acute in disputation, always winning, never bested by anyone. He could speak, write, read and understand Hebrew, Greek, Latin, Arabic and Aramaic perfectly, which was quite amazing in such a young man. When he was sent as an envoy to Pope Eugenius in Rome by the King of Castille he disputed publicly in all the schools of France and Italy and defeated everybody, never being defeated himself by anybody else. At Paris there were various (? why masc) opinions about him, some considering him to be a mage or demon possessed, some the opposite. And there were not lacking those who thought he must be the Antichrist, but this idea is refuted by the man’s life through all Christian things.
A few years later, however, he turned away from all the learning of this world, and bidding farewell to the word for the love of Christ he sailed to the island of Majorca, and became a solitary hermit, serving God Almighty in his holy decision until his death. Before his conversion he wrote certain very subtle commentaries on the Almagest of Ptolemy. He also wrote a beautiful, half prophetical commentary on the Revelation of St John the Apostle. In his hermitage he also wrote many marvelous books whose titles (?) escape my memory. Aside from the book which he entitled Perianacrisis of the good spirit, in two books in a treatise something unknown to me (?). His pupil and inheritor of all his books was Libanius Gallus, the most learned of all the teachers of this age who I have known. I saw several books of holy Pelagius in his possession, which it was beyond my ability to read.