Nerve Agent No 4Nerve Agent No 4 Iris Like Youve Never Smelled Before Every bottle of our perfume contains 10. 75% orris butter, a concentration so rare its almost unheard of. 1. 5 kg of dried iris roots per bottle Each bottle contains the aromatic equivalent of approximately 4 5 mature iris plants, cultivated and aged over several years before being transformed into precious orris butter. In context: Typical perfumes: 0. 010. 3% (iris noticeable) Luxury perfumes: 0.