7. If the card is stationary and the child moved, and if only one size of the letter is used, put in the denominator the number of feet at which the normal eye should see clearly, and in the numerator the distance at which each eye and both together can easily see.
"Civics and Health"
William H. Allen
The punches, belonging to the fifth, are marked on the said scrowl, by the revolutions of the vane, which are accounted by a small numerator, standing at the top of the clock-case, which is moved by the vane-mill.
"The Introduction of Self-Registering Meteorological Instruments"
Robert P. Multhauf
The fractions refer to books in your library-the numerator being the book-number, the denominator referring to the page.
"The Art of Public Speaking"
Dale Carnagey (AKA Dale Carnegie) and J. Berg Esenwein