His analysis of nature informed his art, which informed his analysis of nature… Nothing in nature, he realized, has precise mathematical lines or boundaries or borders. “Lines are not part of any quantity of an object’s surface. Nor are they part of the air which surrounds this surface,” he wrote. He realized that points and lines are mathematical constructs. They do not have a physical presence. They are infinitely small. The line has, in itself, neither matter nor substance and may rather be called an imaginary idea than a real object. And this being its nature, occupies no space.
Source: Leonardo da Vinci – Walter Isaacson