Oats, harvested and dried at their peak milky stage.  My favorite way to use is to steep about 1/4 to 1/2 cup of oats into a quart jar, like you would make any herbal tea, and place in the refridgerator once cooled overnight.  Enjoy your cold infusion the following day after straining the oats.  "One of the best nutritive tonics for the nervous system" pg. 181 Rosemary Gladstar's Medicinal Herbs, A Beginners Guide.