White light, aprox 10 to 15 miles away, moving in the formation of a square.

I saw this years ago at my cousin's house.  I have told lots of people about it but never officialy reported it, because I did not know how.  And of course we did not have the internet back then.  I am guessing on the year because it was so long ago. It was in the summer around 1979, give or take a year.  We were at my cousins house in Lake Tamarask, CA, just North of Desert Center, CA.  We were in the front yard looking North against the mountains.  The mountains were at least 15 or more miles North of Lake Tamarask.  At the base of the mountain was a single white light.  It had to be a fairly large light because at that distance a vehicle light would have been hard to see.  From where we were at the light looked about the size of a dime.  The light was moving in the formation of a square, and again from where we were standing it was a small square, about a foot long by 3/4 of a foot high.  But in reality the distance had to be quite a large distance since the light was so far away from where we were. I am guessing it had to have been at least a mile or more it was moving.  The kicker is that it was moving very fast and at that distance there is no way that a vehicle or normal aircraft could move that far that fast and turn such sharp corners.  My older sister, and my cousing who is about 12 years older than me was also watching this, and I am sure there were more people watching but I cannot remember who. We were all very baffled by this and could only assume it was something not of this world.  I can still visualize this in my mind like it was yesterday.