This unique self-portrait, also known as "view from the left eye", is the creation of Austrian physicist and philosopher Ernst Mach, noted for his contributions to physics such as the Mach number (which relates an object's speed to the speed of sound) and the study of shock waves. The sketch appears in Mach's The Analysis of Sensations, first published in German in 1886 as Beiträge zur Analyse der Empfindungen, and is used to illustrate his ideas about self-perception.
The considerations just advanced, expressed as they have been in an abstract form, will gain in strength and vividness if we consider the concrete facts from which they flow. Thus, I lie upon my sofa. If I close my right eye, the picture represented in the accompanying cut is presented to my left eye. In a frame formed by the ridge of my eyebrow, by my nose, and by my moustache, appears a part of my body, so far as visible, with its environment. My body differs from other human bodies beyond the fact that every intense motor idea is immediately expressed by a movement of it, and that, if it is touched, more striking changes are determined than if other bodies are touched by the circumstance, that it is only seen piecemeal, and, especially, is seen without a head. If I observe an element A within my field of vision, and investigate its connexion with another element B within the same field, I step out of the domain of physics into that of physiology or psychology, provided B, to use the apposite expression of a friend of mine made upon seeing this drawing, passes through my skin. Reflexions like that for the field of vision may be made with regard to the province of touch and the perceptual domains of the other senses.
In order to illustrate in a humorous manner this philosophical "much ado about nothing," and at the same time to shew how the self-inspection of the Ego could be really "carried out," I embarked on the above drawing. Mr L.'s society was most instructive and stimulating to me, owing to the naivety with which he gave utterance to philosophical notions that are apt to be carefully passed over in silence or involved in obscurity.
According to John Michael Krois the "Mr. L" in question is Mach's colleague at Prague University, Prof. Hermann von Leonhardi, son-in-law of the Kaul Christian Friedrich Krause mentioned. Krois also tells us that this original drawing sketched in 1870 in fact differed from the woodblock of 16 years later — the right arm with pencil is absent, with a left arm instead brandishing a cigarette (which has found its way to the mouth in the 1886 image), and a steaming cup of Viennese coffee sits on a small table.