In the front of the topic you will find a symbolic representation of ajna chakra. In the centre is the symbol of AUM, the bija (seed) mantra of this chakra.
In the centre of the diagram there is the black itara lingam. The Sanskrit word itara means ‘another’, or ‘the other, different from’. And this is a perfect description, for it indicates that this lingam is the entrance to the para lingam of the sahasrara. The itara lingam of the ajna chakra is different from but leads directly to the ultimate lingam.
The ajna has two lotus petals, one inscribed with the sun and the other with the moon. These two petals and the sun and moon represent the pingala and ida nadis respectivelv. Two mantras are also inscribed on each petal: (ham) and (ksham). These are the two mantras for Shiva and Shakti, which merge at the ajna.
Ajna has the same implications as the cross: effacement of ego and union of opposites. It was at the centre of the cross that Christ was crucified, transcending his ego and the level of ajna chakra.
Ajna is widely associated with the planet Jupiter, for this planet represents the guru. In the Vedas, ajna is symbolized by Brihaspati, the guru of the devas. It is also interesting that in alchemy the metal tin represents Jupiter, the guru and wisdom. The metal copper symbolizes the planet Venus and devotion; this devotion is that of the disciple. The combination of these two metals, tin (guru and wisdom) plus copper (the disciple’s devotion), produces the well known alloy bronze. This bronze is the metal of initiation and the link between the guru and disciple. This link arises most directly at ajna chakra.
The trigger point of ajna chakra is located at the top of the spine in the centre of the head. It lies in the region of the medulla oblongata and the pineal gland. If you look in a physiology textbook you will get a clear idea of the physical location.
The bhrumadhya, the direct trigger or switch of ajna, lies in the centre of the two eyebrows on the forehead. Ajna lies directly and horizontally behind the bhrumadhya. A drop of tiger balm, camphor, etc. can be placed at the eyebrow centre to intensify perception of the exact location of the bhrumadhya.