Many of the Sareoso diagrams incorporate seven-sided sigils, shapes made by connecting seven points equally spaced around a circle in different ways. The diagrams below shows three of the simplest shapes, which I call the three mothers:
As you can see, the three are made by spacing out the points that one line joins together. In the first diagram, two adjacent points are joined, in the second one there is a gap of one point, and in the third one a gap of two points. If we were to carry on, leaving a gap of three points, we’d find the shape would be the same, but drawn backwards.
There’s an interesting effect when we superimpose all three diagrams. We get a seal made of 21 connections.
Looking at the seal you can see that each point is connected to the six other points in the circle. Seven points connected to 6 other points gives 7×6=42 ways of going between points, but because each path is counted forwards and backwards, the total number of connections is 42÷2 = 21.
This connection of the three sigils with the 21 is hinted at in diagrams 14 and 22.
If you want to draw your own seven-sided sigils, you can use the construction method hinted at in diagrams 12 and 13 to make a quite accurate seven-sided shape (heptagon), using the approximation attributed to Albrecht Dürer. The method is described here: