Based on the principle of the stereoscope invented in the 19th century, this wall-mounted instrument presents viewers with two photographs taken simultaneously with two cameras in eye-width proximity to one another. A wall, invisible to the viewer, divides the photographs. The resulting image appears to be three-dimensional. Several images can be seen in the instrument, one after the other; the subject of these are the patterns produced by the three-dimensional version of the harmonograph (see The endless study in three dimensions series, 2006).