From an issue of The American Agriculturist, from the 1880s

The accompanying engraving shows how easily a serviceable Level may be constructed with an ordinary carpenter's square, a short plumb-line, and a sharpened stake. The stake, with a split in the top, is driven into the ground, and the square adjusted as shown in the engraving. For the plumb-line, a string and a piece of lead, or, in an emergency, even a stone, for the plummet, will answer. The line is fastened to the shorter arm of the square, so that it will run close to and parallel with the inner edge of the longer arm. As the two arms of the square are at right angles, when the longer one is perpendicular, as determined by the plumb-line, the shorter one is horizontal or level. Any objects sighted along the upper edge will be in the same plane, or on the same level.


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