The Origins of Wonder
While this effect has commonly been said to be an invention of Buatier deKolta in 1875, it was performed by J. N. Hofzinser in Austria in the early 1860s or before. Hofzinser produced eight balls in his bare hands, using a Ball Shell as an aid. The multiplication was effected within the hands, rather than between the fingers. What few details are known about Hofzinser's routine are given in J. N. Hofzinser: Non Plus Ultra, Vol. 3, by Magic Christian, 2012, Section 3.2, p. 76.
DeKolta's method is reported to have used a gimmick made of two half balls hinged together, which when closed appeared as one ball, and when open was displayed as two. Others record that two hinged hollow half shells were used. DeKolta may have employed both. In More Magic, 1890, p. 261, Professor Hoffmann credits deKolta as the originator of the trick and teaches routines by Professor Hellis and himself, which involve the production of a ball, its multiplication and then the disappearance of the balls, one by one. These two routines limited themselves to the production of just three balls. The multiplication still occurred within the hands. The apparatus described does not use hinged half balls or hinged shells. Instead, two separate half shells were employed, which fit over a solid ball and were joined loosely together like a box and telescoping lid. In Hoffmann's routine, a set of nesting smaller balls was also used, to add a diminishing-ball sequence to the disappearance of the last ball. The details of deKolta's routine were apparently not known to Hoffmann.
Another style for effecting the multiplication on the balls in the hands is described in the January 1893 issue of La Nature, No. 1025, p. 128. Here, a fan was waved in front of the ball while, undercover of the fan, the solid ball was separated from the shell. The handling described here and that by Hoffmann were probably related to or outgrowths of techniques used roughly thirty years earlier by Hofzinser.
In 1898, August Roterberg released the “Excelsior Ball Trick”, a version of the Multiplying Billiard Balls using just one half shell, with the balls appearing between the fingers rather than within the hands. This handling soon grew to become the standard method and has remained so to the present day. Roterberg was commonly given credit for it, but almost half a century later the true originator became known: George Wright, who came up with the method while working for Roterberg in Chicago. He told his story in Munroe's Magical Miscellany, No. 36, Jan. 1946, p. 8.