We explored size-distance scaling with a demonstration based on the classic Holway-Boring experiment. Undergraduate psychology majors estimated the sizes of two glowing paper circles under two conditions. In the first condition, the environment was dark and, with no depth cues available, participants ranked the circles according to their angular sizes. In the second condition, the environment was illuminated and, with depth cues available, the students ranked the circles according to actual physical size. The demonstration replicated the key elements of the original experiment, and objective and subjective measures indicated that it improved understanding of size-distance scaling. We also describe variants of the experiment suitable for different instructional environments. (Contains 3 figures and 1 table.)