Age-old magical effects lie hidden in this symbol, for it is derived from the ‘protective circle’ or ‘charmed circle,’ whose magic has been preserved in countless folk customs. It has the obvious purpose of drawing a sulcus primigenius, a magical furrow around the centre
Jung establishes that the mandala’s psychological efficacy derives directly from the ancient magic circle tradition, tracing its protective function to the ritual sulcus primigenius drawn around the temenos of the innermost personality.
, Alchemical Studies, 1967thesis