The Third Eye of Shiva [Triyambaka] is set mid-point on the forehead, equidistant from the two corporal eyes.
It stands unprotected, does not blink, is never closed.
In its proper mythic interpretation, the Eye carries no eyelid [an irregularity quickly corrected by Bollywood poster-artists].
‘If the eye never sleeps, all dreams will naturally cease’ notes the Hsin-hsin Ming. [Keep in mind though that there is nothing wrong with dreams. Nice dreams and not-so nice dreams.]
When Hui-neng, the defining sixth patriarch of C’han-Zen arrived on the scene, the traditional practice was to ‘cleanse one’s eye’ until one see’s the immaculate purity of Self-Nature. With Hui-neng, the old symbol of ‘K’an-ching‘, to keep an eye on purity, became ‘Chien-hsing‘.
The former symbol was that of ‘hand and eye’, the separated observer, while Chien-hsing, an eye alone, was pure un-bifurcated ‘Seeing’. It becomes a principal name for Satori [‘Enlightenment’].
And it halted the Tradition from sinking, as had happened to so many others, into a passive contemplation. But there are examples aplenty where ‘hsing‘ and its variants [fo-hsing: Buddha-Nature; fa-hsing: Dharma-Nature, etc.] are reduced to exactly that.
The Third Eye has been incorporated into the Puranic Literature in a myriad imaginative ways [Kamadeva, Trimurthy, et al].
And it has had a wide field of play, from early Buddhist [Swayambunath, Kathmandu] to the Freemason Pyramid’s: ‘Eye of Providence’, atop the isosceles edges of an equidistant base, which thanks to the philosophical orientation of the Founding Fathers can be found on the Great Seal of the United States and the One Dollar Bill.
Quite a journey.