Help with Echinacea tincture

Hello!

I would like to make a supply of Echinacea tincture. Since Echinacea is not as common and easy to get where I live, I will have to order from an online store, which took quite some time to find.

I would like to order the right amount of echinacea root for my needs. Can anyone estimate how much Echinacea root (in pounds or kilos) I will need, if I want to make 6 liters (=1.6 gallons = 203 oz) of Echinacea tincture. - If I could just go to a store and see the Echinacea root, I could easily estimate myself, how much I would meet. - But since I have to order online and the Echinacea is quite expensive, any help would be greatly appreciated.

Many thanks,
Solmare