The Dynkin diagrams of type ADE are ubiquitous in mathematics as solutions of various classification problems. The diagram E6 is usually drawn by five dots in a row with a sixth dot above the third, see for example here. There would be many other ways to draw the diagram E6, for example the sixth dot below the five dots, or just a capital
E.
Is there a reason for drawing that diagram in that particular shape beside or is that just a confirmed habit?
