The picture Veil of Veronica by Claude Mellan (1649) is drawn with one single line that only varies in width! Starting from the nose it moves outwards in a spiral. This line is modulated varying in width. I was executed with machine aid not completely manual.

It is difficult to see in the picture, i know. But the picture IS INDEED drawn in one, single modulated line. The icon on the chapter page up is a zoom of the spiral beginning at the nose.

Line as sign
dots and lines (an interupted line) may resemble code - morse code.
This code-language contains meaning.