His ordinary drink was water, and to this habit he attributed not only his length of years, but also the extraordinary excellence of his eyesight. Till recently, a curious relic of Locke's water-drinking habits was preserved in the shape of a large mortar of spongy stone, which acted as a natural filter, and which he used to call his brew-house. He was assiduous in taking exercise, and was specially fond of walking and gardening. In the latter years of his life he used to ride out slowly every day after dinner. When advising his friend Clarke about his health, he says, "I know nothing so likely to produce quiet sleep as riding about gently in the air for many hours every day," and then, like a truly wise doctor, he adds, "If your mind can be brought to contribute a little its part to the laying aside troublesome ideas, I could hope this may do much." At last, when he was no longer able to sit on horseback, he commissioned Collins to have an open carriage specially made for him, the principle on which it was to be constructed being that "convenient carries it before ornamental." In November, 1703, the Heads of Houses at Oxford--who at that time constituted the governing body, and through whose repressive and reactionary administration the evil genius of Laud then and long afterwards continued to cast a blight on the University--resolved to discourage the reading of Locke's _Essay_. The attempt was futile, as they relied, not on coercion, but on the influence of their authority, which appears to have been held very cheap. Locke was now far too eminent a man to be troubled by so anile a demonstration of folly. "I take what has been done as a recommendation of my book to the world," he says, in a letter to Collins; and then he promises himself and his friend much merriment on the subject when they next meet. Locke's last literary labour appears to have been his _Fourth Letter for Toleration_. Jonas Proast, after a long interval, had returned to the charge in a pamphlet published in 1704; and Locke, unfortunately, thought it incumbent on him to reply, though he had long ceased to pay any regard to the assailants of the _Essay_. The _Letter_ is unfinished. Its last words cannot have been written long before Locke's death.