| Description | On the ibn al-Haytham / alhasein / alhazen problem.
This is a figure relating to Christian Huygens's treatment of Alhazen's problem, which was enclosed with his letter to Henry Oldenburg dated 26 June 1669.
Diagram consists of two circles with angle lines drawn across them.
The diagram and text are printed using a method that Huygens claimed he had invented, making the acid bite all the way through the plate and inking over it, as with a stencil.
Subject: Geometry
Published in Philosophical Transactions as 'Excerpta ex epistolis non-nullis, ultrò citróque ab illustrissimis viris, Slusio & Hugenio, ad editorem scriptis, de famigerato albazeni problemate circa punctum reflexionis in speculis cavis aut convexis; & primò quidem ex prima Hugenii'. |