My trusty Alain Paris "Dictionnaire des Interpretes" says [in French] that
it was in Brazil on 30 June 1886 when Toscanini [19 years old & engaged
to assist in rehearsals during a Brazilian tour] took the baton after the
failure of several other conductors and directed Aida from memory.  It was
such a triumph that the impresario had him conduct the other twelve operas
in the repertoire for the remainder of the tour.

Regards,

Bill Karzas                     [log in to unmask]