56х56 sm (22x22")
Decimal system, generally accepted today, is neither the first nor the only one. There were other ways to count singularl items – not by tens, hundreds, thousands, and so on. Or, for example, by sevens. Four times seven days make about one lunar month. And seven times seven sevens days and three more sevens – a year without a one day. Zero day, for the celebration.
Septenary system is not more or less convenient than decimal. It is just different. They say its origin is astronomic. And where there was astronomy in ancient times, there had always been some mystery and magic.
Arithmetics of 7, related somehow to the very basics of the sum of things, can produce harmonic visual images. For example, “curl of wave”, known from ancient times. We call it classical and "Greek", but it is known long before the Greeks.
Seven items, corresponding in lenth to 1, 2, 3, 4, 5, 7, and placed in a certain way, easily form this vey figure. Symbol of harmony of the Universe? Spiral of time? Or just a simple geometric pattern? Those who want to argue seem to have a good pretext for debates.
But artists just depict things, not necessarily fully understanding the depth of the meanings behind. Seven elongated objects, corresponding to the numbers from 1 to 7. Beautiful ancient symbol, though the meaning is not clear. Even if they are just stones of quite irregular shape simply laid on the ground. Here is the harmony of septenary system.