It has long been a joke that circulates among musicians about ballet dancers, that they only can count to four, not three, and five is right out. So, when they dance a waltz or a tango or something else in three, they go:

"One.. Two.. Three-four.. One.. Two.. Three-four.. "
Should they actually have to dance to a piece in five, say for example, the waltz from Tchaikovsky's Sixth Symphony, (god forbid anything modern), they go:
"One.. Two.. Three.. Four.. And.. One.. Two.. Three.. Four.. And.. "
Six is surprisingly tenable for the ballet dancer:
"One.. Two.. And.. Three.. Four.. And.. One.. Two.. And.. Three.. Four.. And.. "

It is surely apocryphal, but it is said that during one of the orchestra and ballet rehearsals leading to the premiere of Le Sacre du printemps, the composer Stravinsky stood off-stage with the choreographer Nijinsky as the latter shouted numbers to the dancers who were having difficulty finding the beat during some rapid changes of time signature. Nijinsky was shouting numbers that had little relation to the number of beats in each measure, Stravinsky must have thought. And so Stravinsky began to loudly shout "Di.. ag.. gil.. lev.. Di.. ag.. gil.. lev.. ", counting in four the name of the impresario of the Ballets Russes.