This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
A very simple and sufficiently accurate way of enlarging pictures by means of a pencil holder and elastic is shown in the illustration. The picture to be enlarged is fastened to a table top or drawing board, and the paper on which it is to be drawn is placed directly below it. A small brad or tack is driven into the board at A, the location depending on the desired size of the enlarged picture, and the elastic is attached to it. The pencil holder B is fastened to the other end of the elastic over the drawing paper. A pointer, or a knot, is placed in the elastic at C. The pencil holder consists of a stick of wood turned into a handle with a hole bored centrally for a pencil.
In use, the pencil is moved over the drawing paper while the knot or pointer is watched, to keep it following the lines of the original drawing. The stretch of the elastic is sufficient to enlarge the parts equally, as well vertically as horizontally. - Contributed by Wm. Weitzsacker, Buffalo, N. Y.
The Size of the Enlarged Picture Depends on the Length of the Elastic and the Spacing of Pencil and Pointer