Feathers! 

The theatre collection of the Allard Pierson holds many feathers which can be found in design drawings, accessories or as a main component to costumes. Birds and their feathers symbolise freedom and even supernatural powers, but also power and vanity. Dramatists used to make eager use of real bird feathers, but today costume designers often choose synthetic feathers. Before synthetic materials were invented, the popularity of feathers almost led to the extinction of some bird species.