Escher was fascinated by unusual vantage points and something he has described as “mental imagery” often based on theoretical premises. The litograph Hand with Reflecting Sphere, also known as Self Portrait in Spherical Mirror, depicts a hand holding a reflective sphere where we can see the artist and his surroundings. Self portraits in reflective convex surfaces were very common in his work and this piece is certainly the most famous example. In this pieceEscher does the unusual and shows the means by which all self-portraits must be created. He makes the mirror the subject of his piece. He is less interested in his own image, but the way the space is distorted by a convex reflective surface. (http://www.widewalls.ch/famous-self-portraits/m-c-escher-hand-with-reflecting-sphere-1935/)