When you have run the length of various practices and none of those practices remain in your mind, that very lack of mind itself is the heart of "all things." When you have exhaustively learned the various practices and techniques and made great effort in disciplined training, there will be action in your arms, legs, and body but none in your mind; you will have distanced yourself from training, but will not be in opposition to it, and you will have freedom in whatever techniques you perform. You yourself will be unaware of where your mind is, and neither demons nor heresies will be able to find it.

— Yagyū Munenori, The Life-Giving Sword