Abstract
In one of Leonardo Da Vinci's notebooks, an experiment is described where strengths in tension are measured for various lengths of wire. The notebook indicates that the results of these experiments were that longer wires were weaker than shorter wires. This result defies classical mechanics of materials. This conflict has been explained as a note-taking failure by Leonardo. This short note develops an alternative explanation, based on the likely heterogeneity of the mechanical properties of the wire and elementary probability theory. This latter explanation has implications for the difficulty and delays experienced by early investigators into the mechanics of materials.