It is related to regular pentagons and pentagrams, which are known in Sumerian tablets as early as 3200 BC.

• 民间大都知道“九五之尊”的说法，故宫的建筑的确与“九”和“五”两个数位有关联，如天下闻名的天安门城楼其城台设五个门洞，面阔九间，进深五间。