Culpeper's Complete Herbal: The Cure of all Disorders Incident to Mankind

All other Authors that have written of the nature of Herbs, give not a bit of reason why such an Herb was appropriated to such a part of the body, nor why it cured such a disease. Truly my own body being sickly, brought me easily into a capacity, to know that health was the greatest of all earthly blessings, and truly he was never sick that doth not believe it. Then I considered that all medicines were compounded of Herbs, Roots, Flowers, Seeds, &c. and this first set me to work in studying the nature of Simples, most of which I knew by sight before; and indeed all the Authors I could read gave me but little satisfaction in this particular, or none at all.