Some cultures have even begun to expand social prohibitions on female toplessness to prepubescent and even infant girls. This trend toward covering the female nipple from infancy onward is particularly noticeable in the United States. [Allen, Anita L. (20
The exercise ball was developed in 1963 by Aquilino Cosani, the first ones were much smaller and used in treatments for infants and newborns. [wikipedia]
The nipple is a raised region of tissue on the surface of the breast from which, in females, milk leaves the breast through the lactiferous ducts to feed an infant.