Among these Artes, by good reason, Perspective ought to be had, ere of Astronomicall Appearences, perfect knowledge can be atteyned. And bycause of the prerogatiue of Light, beying the first of Gods Creatures: and the eye the light of our body, and this Sense most mighty, and his organ most Artificiall and Geometricall. At Perspectiue, we will begyn therefore…. This art of Perspectiue, is of that excellency, and may be led, to the certifying, and executing of such thinges, as no man would easily beleve: without Actual profe perceived. I speake nothing of Naturall Philosophie, which, without Perspectiue, can nor be fully vnderstanded, nor perfectly atteined vnto. Nor, of Astronomie: which, without Persepective, can not well be grounded: Nor Astrologie, naturally Verified, and auouched. John Dee, Mathematical Preface