The tale of a Divine tortoise

This pic I took under the tortoise which has the magic square with numbers. I was wondering at that time why and what is it significance. Then I searched the net and found that approximately 5000 years ago, the chinese emperor "Yu" saw a divine tortoise in the Yang-tse river. Here did you notice the sum in all the staright lines is 15. Does the divine tortoise want to convey any message to the emperor.

This is the tortoise he found from which he picturised the dots into numbers and finally summed them which was a mistery for him at that time. What exactly he got from analysing this dots on a divine tortoise.

Here is the full story for you http://mathforum.org/alejandre/magic.square/loshu2.html