-Letter of 13 March 1647 (from Florence to Rome): "Passignanum conveni, et simul Datum adduxi quo melius mentem nostram dissimularemus, et de pretio nummorum stricte disseruimus, et dubio procul nos conventuros confido, quod omni ut maiori fiat compendio curabo. Proxima, quam ad te mittam epistola statutum pretium, pondusq. adamussim docebit. Interim cum argentario ad eum accedam, auroque indice tacto extremam huic negotio manum imponam; ac de omnibus te certiorem faciam. Libros de re nummaria, si quos habebit, faciliter impetrabimus, vereor tamen apud eum non esse. promisit Thomas se diligenter perquisiturus et si extabunt, non denegabit. Scriptores de hac re (ut optime calles) Goltzius, Biragus, et Auctor Promptuarij, omnes sua volumina ultra montes edidere; quae omnia faciliter habere poteris. In Italia unus, quod sciam Aeneas Silvius Parmensis (nb: A mistake for Vicus = Vico), antiquitatis doctissimus, et accuratus librum suum in Italia typis mandavit, et raro invenitur, cum apud peritos maximo in pretio sit; quem aliquo ab humanitate tua temporis spatio impetrato dabo operam ad te perveniat.
I met Passignano, and at the same time I took Dati so that we could better disguise our intentions, and we briefly discussed the price. I am confident that we will certainly agree, which I will take care to do with the shortest possible time. The next letter I send you will tell you exactly the agreed price and weight. Meanwhile I will go to him with a goldsmith, and, having had the gold tested with a touchstone, I will put the last touch on this business. And I will inform you about everything. We will easily procure his books on numismatics, if he has any, but I am afraid that he will not have any. Thomas promised that he would would look out for them and, if there were any, he would not refuse them. The relevant authors (as you know very well), Goltzius, Mediobarbus, and the author of the Promptuarium all published their volumes on the other side of the Alps, and you will easily be able to get them all. In Italy there was only one, as far as I know, Enea Silvius of Parma, who was very learned about ancient world and who carefully entrusted his book to the press in Italy. It is rarely found, since it is in valued very greatly by experts, and I will take care that, if I can be allowed some time by your generosity, it will come to you." (Leiden University Library MS BPL 1920, van Cavalcanti no 3)