The three sites of Bharhut, Sanchi, and Mathura, have yielded huge numbers of Yakshi figures, most commonly on the railing pillars of stupas. These show a clear development and progression that establishes certain characteristics of the Yakshi figure such as her nudity, smiling face and evident (often exaggerated) feminine charms that lead to their association with fertility. The yakshi is usually shown with her hand touching a tree branch, in a sinuous "tribhanga" pose, thus some authors hold that the young girl at the foot of the tree is based on an ancient tree deity.