UNDERSTANDING is the ability of the mind to know or to comprehend  God as supreme knowing.  The Revealing Word says “SPIRITUAL UNDERSTANDING is the quickening of the Spirit within.  Spiritual understanding is the ability of the mind to apprehend and realize the laws of thought and the relation of ideas one to another.”
INTELLECTUAL UNDERSTANDING comes first in the soul’s development, then a deeper understanding of Truth principles, which, in turn, opens the way for revelation.  The DISCIPLE who represents understanding is Thomas which means joined, conjoined, twin.  Thomas represents reason and intellectual perception; and is called the doubter because has to see in order to believe in the resurrection.

LOCATION IN BODY:  Front brain.

Einstein says, “Every man knows that he does best in his work and accomplishes most when he has attained a proficiency that enables him to work intuitively.”  Twelve Powers of Man.  

The OIL associated with UNDERSTANDING is ONYCHA.
ONYCHA (Styrax benzoin), an absolute extraction from the resin of the benzoin tree, dark sage green about three feet tall.  Native to India, China, Laos, Thailand, Vietnam.  Most viscous of all oils consisting of Di and Tri Terpenes, heavier than mono or sesquiterpenes.
HEBREW  root sh cheleth, meaning aromatic shell; fingernail in Greek since the resin is sometimes translucent like a thick fingernail.

BIBLE REFERENCES:  Exodus 30:34 (Then the Lord said to Moses, “Take fragrant spices—gum resin, onycha and galbanum—and pure frankincense, all in equal amounts, and make a fragrant blend of incense, the work of a perfumer. It is to be salted and pure and sacred); Sirach 24:15 ( Like cinnamon and acanthus, I have yielded a perfume, like choice myrrh, have breathed out a scent, like galbanum, onycha, labdanum, like the smoke of incense in the tent); Genesis 1:14-19 (fourth day of creation); Exodus 28:30 (Also put the Urim and the Thummim in the breastpiece, so they may be over Aaron’s heart whenever he enters the presence of the Lord. Thus Aaron will always bear the means of making decisions for the Israelites over his heart before the Lord.)
ONYCHA is associated with Egyptian god Khepra or Ra, sun god, who pushes the sun (enlightenment) across the sky.
In the TAROT,  ONYCHA is the perfume for the path of the charioteer between Binah (understanding) and Tiferet (balance).  The charioteer’s emblem is the sun; behind him on the card is the moon (will); he gives understanding to the Fool about how to defeat an enemy.  The black and white horses that the charioteer directs (representing the subconscious and conscious mind) draw in unison.  An understanding of Truth inspires a willingness to follow its path.

ONYCHA  is also the name of membrane that functions as a door into the interior of  a shellfish. Just as understanding progresses from the head to the heart, so too the scent of onycha is associated with the path from Binah (understanding) to Tiferet (the heart center).