Ohh yer sorry, its an 1/8 of a cup of ginger powder. Yes its readily availiable from "most" Grocery stores, you can also use fresh ginger too, just grate some up and away you go.
It was a great experience for me, i woke up feeling re-freshed and like i had been asleep the whole night, as normaly i sleep terribly. I will be doing it again next Saturday night.