Observatio & demonstratio cometae aetherei, qui anno 1577 et 1578 constitutus in sphaera veneris, apparvit, cum admirandis eius passionibus, varietate scilicet motus, loco, orbe, distantia à terrae centro, &c. adhibitis demonstrationibus geometricis & calculo arithmetico, cuiusmodi de alio quoquam cometa nunquam visa est

These are such monuments, whose honor and praises will remain perpetually, and which are placed in the grateful mind of all posterity like a high pyramid that will never collapse or perish.

But if the future age attributes the due glory to Your Highness for these distinguished and noble benefits and considers you worthy of immortality, certainly the men of the present age, who enjoy this very piety of their Prince, will not show themselves ungrateful, but will return the greatest gratitude they can. Especially will this be fitting for those who, by this liberality of Your Highness, have been so inclined that they have not only recognized the true light of the Gospel themselves, but can lead others to the same and win many for Christ.

They will never return a reward that is truly equal. For who would dare to presume that they could compensate God the Creator, or their Prince, and their parents for the benefits they have conferred? Yet one way, while others are closed, lies open for rewarding them, which is that they should declare themselves mindful with a grateful heart. Besides this, God, from whom we have ourselves and all our things, demands that nothing else be returned to Him than that He be loved by us with all our heart, with all our soul, and with all our strength, and that He be invoked in the day of tribulation, and glorified. Parents also, who spare no labor or sorrow for the sake of their children's salvation, consider the gratitude repaid excellently if they see that they are loved in return by their children, and that they obey their precepts. Thus also, the fathers of the fatherland who bear the scepters, upon whom all safety of the state depends, judge benefits returned with interest when they observe that their subjects respond with love and faithful obedience. Therefore, Your Highness's subjects will perform this same thing for you, being mindful of the benefits received with a grateful heart, and testifying by words and deeds that these were not bestowed upon the unworthy.

Among the number of these, Most Illustrious Prince, most clement Lord, I also find myself. For besides the fact that by the Most Illustrious Prince original: "Christophoro" Christopher, of happy memory, Your Highness's progenitor, I was received from almost my tender years into the bosom of the Church and Schools, and was mentored in the studies of letters: through the liberality and stipends of Your Highness, I arrived at a point where I could engage in leisure, not only in philosophical arts and sciences, but especially in those that savor of the Mathematical—to which I believe I was born, since I have been so delighted by their knowledge since boyhood by a certain natural and secret ardor, that even now no distaste for them arises in me—but also I was able to give attention to the salvific doctrine of the most holy divine word, as much as the grace of God has granted me.