The Claude glass. Use and meaning of the black mirror in Western

"many are familiar with the Claude glass as a small black convex mirror used by artists ans spectators of landscape to reflect a view an make tonal values and areas of light and shade visible. Millet [...] goes beyond this particular function of the glass ans situates it within a richer archaeology of Western thought, exploring the uncerntainties ans anxieties about mirrors, reflections and theri potential distorsions".