Abstract: A base defines a pair of horizontally spaced apart front and rear anchor points and a pair of front and rear elongated, upstanding and upwardly divergent support links and have the upper ends thereof pivotally anchored to the front and rear anchor points for oscillation about first parallel axes extending transversely of the links. A support member, including a pair of horizontally spaced apart front and rear anchor locations, is also provided and the lower ends of the front and rear links are pivotally anchored to the front and rear anchor locations for oscillation about second axes paralleling the first axes. A seat structure is supported from the support member in elevated position relative to the latter and the first parallel axes.