Original: It was originally scored for a chamber group of flute/piccolo, clarinet (B flat and C), two pianos, glass armonica, xylophone, two violins, viola, cello and double bass, but is usually performed today with a full orchestra of strings, and with a glockenspiel substituting for the rare glass armonica.
Simplified: Saint-Saëns arranged it for an orchestra consisting of  flute doubling piccolo, clarinet (B flat and C), two pianos, glass harmonica, xylophone, two violins, viola, cello and double bass.