Several people have asked me how kamon were designed and drawn in the past. Well the answer is with ink, rulers, compasses and a bit of free hand drawing. Since most kamon are based on circles and symmetries, the ability to divide a circle in 2, 3, 4, 5 or more equal parts is very important.
To give a quick idea of kamon geometrical complexity, I attached with this post some pages from a 19th century Bukan (mon encyclopedia) that give some insight in the way mon were created.
Translating the text would be too difficult, but illustrations are worth a 1000 words, so I hope it will help.