We studied the effects of viewing François Morellet's Triple X Neonly (2012) on postural control and subjective appreciation. Triple X consists of 6 neon tubes arranged in a corner into a triple X pattern. Twenty-one participants were asked to view it with only one eye open (monocularly) and with both eyes open (binocularly). Their average forward-backward (anteroposterior) body sway root mean square (rms) velocity was significantly greater viewing it monocularly than binocularly. There were also large differences between subjects during monocular viewing for three of the six measured postural parameters (rms side-to-side (mediolateral) velocity, rms side-to-side displace-ment, and rms normalized area of the movement of the locus of centre of gravity). The participants showed very diverse subjective reactions to the artwork, yet their comments mainly concerned its apparent movement and depth. We conclude that binocular viewing allows the viewer more easily to appreciate the proximity of the central X, thus requiring less energy to keep the body stable. This study confirms the artist's success in involving viewers actively in their aesthetic experience: through their eye and body movements, the work engages them to actively contribute to the work itself.