Carman, John Hendrix: Renaissance Theories of Vision. Niels Lyhne Nikola Tesla tells his son Leonid that the three represent the branches of time, what is, what has been before and what will be. Pest und Corona He argued, using a physical analogy, that perpendicular rays were stronger than oblique rays: in the same way that a ball thrown directly at a board might break the board, whereas a ball thrown obliquely at the board would glance off, perpendicular rays were stronger than refracted rays, and it was only perpendicular rays which were perceived by the eye.Retrieved 22 October 2014.
The first theory, the emission theory, was supported by such thinkers as Euclid and Ptolemy, who believed that sight worked by the eye emitting rays of light. Zwischen mir und dir In: Helaine Selin (Hrsg. Kalte Seele, dunkles Herz Oxford University Press, 23.The second theory, the intromission theory supported by Aristotle and his followers, had physical forms entering the eye from an object.