Source, in full
First appearance on google books is C. Edwards Lester's 1845 English translation of Ansaldo Ceba's book Il Cittadino di Repubblica, translated as The Citizen of a Republic, which on p. 92 says "Moderate exercise is also indispensable; its bounds seem to have been fixed by Socrates—'Exercise till the mind feels delight in reposing from the fatigue.'" However, the original Italian version the same comment, found on p. 144 of this edition, does not give this as a direct quote but just as a summary of Socrates' teachings: "L' esercizio moderato della persona, noi crediamo ancora esser utile pel mantenimento della sanità; e il termine di questa moderazione pensiam che per lo più voglia essere quello che statuiva Socrate; cioè, finchè l' animo prenda diletto della fatica." Google translate renders this as "We still believe that moderate exercise of the person is useful for maintaining health; and we think that the limit of this moderation should mostly be that which Socrates established; tha