From Dr. Felix Adler, Moral Instruction of Children, 1912:

...there are influences in manual training... which are favorable to a virtuous disposition. Squareness in things is not without relation to squareness in action and in thinking. A child that has learned to be exact--that is, truthful--in his work will be predisposed to be scrupulous and truthful in his speech, in his thought, in his acts.

And from Charles H. Hamm, Mind and Hand:

It is thus that the trained hand comes at last to foresee as it were that a false proposition is surely destined to be exploded. The habit of rectitude gives it prescience. It invariably discovers, sooner or later, that a false proposition, when embodied in wood or iron, becomes a conspicuous abortion, involving in disgrace both the designer and the maker. A false proposition in the abstract may be rendered very alluring; a false proposition in the concrete is always hideous. One of the chief effects of manual training is, then, the discovery and development of truth; and truth, in its broadest signification is merely another name for justice; and justice is the synonym of morality.