It is most popular vegetable fixative. If you grow in your garden the blue-flowered Iris Florentina, as my friend does, you can prepare your own powder.
"Dig up the roots, peel them carefully, and dry them in the sun. Store them in a dry airy place for a year, or two; the frangance is stronger the second year.
Then grind, or powder them as needed. Save the rest!
About a 1/3 cup is used for 4 to 8 cups of petals."
In London I loved to stop by Culpeper's , named after Thomas the old governor of Virginia as some say- not sure - just to enjoy the fragrances.
But, another Culpeper I believe was the ONE! Must find notes on this one, and will post.
In Florence many old apothecaries carry many of the old fixatives, and in
the States the place to go is Caswell-Massey.