Painters, sculptors, and architects have engaged with balance in their works to present forms that have a tenuous distribution of weight, threatening to become unstable by outside forces. Many of Richard Serra’s monumental steel sculptures present a precarious sense of balance in an effort to explore the physical and psychological effects of space. His One–Ton Prop (House of Cards) (1969), for example, consists of four heavy plates leaning against each other, supported by nothing but pressure. Other artists, like Alexander Calder, use balance to achieve the floating, kinetic effects of his suspended mobiles, such as in Triumphant Red (1959-1965). More figuratively, photographer Michael O’Neill studies tension and balance by portraying bodies in movement and yoga postures.