In a late prose piece, Mallarmé makes the provocative claim that "the ballerina is not a girl dancing".
Indeed, according to Mallarmé, she's not even a girl, but a living metaphor; symbolising "some elemental aspect of earthly form", such as a flower or a swan.
And she doesn't dance so much as use her body - "with miraculous lunges and abbreviations" - to produce and perform a special kind of condensed writing whose ties to a metaphysically stable world of referents have been snapped: une écriture corporelle.
Thus, whilst not quite one and the same thing, ballet and poetry are semiotically entwined; they are both formalised and ritualised aesthetic sign systems, designating truth that is plural and uncertain.
And this is why Nietzsche loved both art forms and not only held great poets such as Goethe and Heinrich Heine in the highest regard, but blessed the feet and fair ankles of sweet girls who, in dancing, transcend their gender and humanity and bring meaning to a crisis.
See: Stéphane Mallarmé, 'Ballets', in Divagations, trans. Barbara Johnson, (Harvard University Press, 2009).