Based on this image of Anna Pavlova wearing a kokoshnik ballet costume, taken either 1909 or 1911, photographer unknown. The costume (designed by Ivan Bilibin) still exists intact, and currently belongs to the Museum Of London.
When I emailed the director of the museum (The Museum Of London) that owns it, they said it was in storage... but then again, that was a few months ago.
(For fear of generating a bad link, I'll just say that if you Google image search "Anna Pavlova kokoshnik", you should see it!)