Letter 15 — On Brawn and Brains (§6)

“Of course I do not command you to be always bending over your books and your writing materials; the mind must have a change,—but a change of such a kind that it is not unnerved, but merely unbent. Riding in a litter shakes up the body, and does not interfere with study; one may read, dictate, converse, or listen to another; nor does walking prevent any of these things.”