Dr. Richard Schulze is one of the foremost natural healers and master herbalists in the world. Keep in mind that he did not create this juice to have as a "tasty treat," but for healing purposes.
His original recipe calls for 2oz of wheat grass instead of kale. We've found that about 2 cups of (packed) wheat grass yields 2oz of juice. You can also find variations of this recipe using spinach, cabbage, dandelion greens, and chard (and other dark green, purple, and deep red vegetables and fruits).