Mercury is a major Roman god, within the ancient Roman pantheon. He is the patron god of financial gain, commerce, eloquence (and thus poetry), messages/communication (including divination), travelers, boundaries, luck, trickery and thieves; he is also the guide of souls to the underworld.He was considered the son of Maia and Jupiter in Roman mythology.In his earliest forms, he appears to share characteristics with the Greek god Hermes. 
Hermes is an Olympian god in Greek religion and mythology, son of Zeus and the Pleiad Maia. He is second youngest of the Olympian gods.Hermes is a god of transitions and boundaries. He is quick and cunning, and moves freely between the worlds of the mortal and divine, as emissary and messenger of the gods, intercessor between mortals and the divine, and conductor of souls into the afterlife. He is protector and patron of travelers, herdsmen, thieves, orators and wit, literature and poets, athletics and sports, invention and trade. In some myths he is a trickster, and outwits other gods for his own satisfaction or the sake of humankind. His attributes and symbols include the herma, the rooster and the tortoise, purse or pouch, winged sandals, winged cap, and his main symbol is the herald's staff, the Greek kerykeion or Latin caduceus which consisted of two snakes wrapped around a winged staff. In the Roman adaptation of the Greek pantheon (see interpretatio romana), Hermes is identified with the Roman god Mercury.
Messenger of Knowledge
In the Greek tradition, Hermes is the messenger of the gods, the one who conveys all the knowledge and wisdom of the gods to the other gods and to human kind, and even into hell.Hermes is also a symbol of that force of divinity that guides those who have died; he guides the dead to their next residence. He also guides souls out of the lower realms. This symbolism represents someone who is dying mystically, psychologically, someone who is sacrificing himself, and destroying and removing all that is impure and animal in order to be reborn as something new. Mercury, Hermes is the one who facilitates that process of thorough change. Hermes is the messenger of divine trinity, the one who conveys the Word. As such, Hermes is able to travel anywhere in the cosmos. He is one of the few in Greek mythology that could enter and leave hell at will. Mercury (Hermes) represents an aspect of ourselves, an aspect of the Divine Being, of true divinity, a living, vibrating, actual force in nature that the Alchemist learns to work with. Mercury (Hermes) is a Principle of alchemy that lives inside of us. The sacred number of Hermes is the number four.
The name of Hermes actually comes from the Greek word herma, which refers to a rectangular or square stone with four sides. A herma is a small stone pillar with a human head on top, and directly in the center is an erect masculine sexual organ. The Hermai were placed at crossroads all over Greece. A cross roads is a cross, an intersection of four directions. The cross is not merely a Christian symbol; it is universal. The Greeks would make offerings to these stones. The hermai were considered so sacred that even in times of war invaders would not damage the Hermai of their enemies. They would destroy everything else, but not the Hermai. That is how sacred they where considered to be, and with good reason. This symbol hides everything about the most sacred heart of the Greek mysteries, and Alchemy, Gnosis, Christianity, Egyptian mysticism, Asian mysticism. The head represents the divinity, the perfected man, the primordial Adam or Albion who comes out of the stone, who is perfected, sculpted, crafted out of the philosophical stone, the philosophical earth. The method to create a perfect being is through a refined use of the same energy we use to create any other being: the erect masculine sexual organ, through sexual energy. A perfect being is created through the upright, proper use of sex, with mindfulness of the Divine, the source of sexual power. So this symbol from the Eleusinian Mysteries is the heart and soul of the Greek mythology. These are mysteries that were never communicated to humanity openly and publicly, until the end of the Ascension Cycle. The herma represents the power of Mercury that is trapped in the stone, the power of the messenger of the gods. That is why the Freemasons utilized the stone as the most fundamental symbol of masonry.The waters in sex, the spine, and the mind are ruled by Mercury. They are Mercurial. In Alchemy, they are symbolized by Mercury.
Hermetically comes from Hermes, Mercury. Gnosis is a hermetic tradition. We are from the tradition of Hermes, Mercury. When you work with Hermes Mercury, your vessel must be perfectly sealed. “Hermetically sealed” refers to our Yesod or 2nd Chakra and sphere. Hermetically sealed means we let no energy escape. We retain our inner creative froces, our sexual energy, the forces of Yesod, the foundation, so that that energy can be used to build our temple from the solid stone in our root .
Hermes Trismegistus is the purported author of the Hermetic Corpus, a series of sacred texts that are the basis of Hermeticism. He may be a representation of the syncretic combination of the Greek god Hermes and the Egyptian god Thoth. In Hellenistic Egypt, the Greeks recognised the congruence of their god Hermes with Thoth. Subsequently the two gods were worshipped as one in what had been the Temple of Thoth in Khemnu, which the Greeks called Hermopolis. Hermetic philosophy rationalized and systematized religious cult practices and offered the adept a method of personal ascension from the constraints of physical being, which has led to confusion of Hermeticism with Gnosticism, which was developing contemporaneously.This last account of how Hermes Trismegistus received the appellation "Trismegistus," meaning "Thrice Great," is derived from statements in the The Emerald Tablet of Hermes Trismegistus, that he knows the three parts of the wisdom of the whole universe. The three parts of the wisdom are alchemy, astrology, and theurgy (divine workings of the Universe).
As a divine source of wisdom, Hermes Trismegistus was credited with tens of thousands of writings of high standing, reputed to be of immense antiquity. Plato's Timaeus and Critias state that in the temple of Neith at Sais, there were secret halls containing historical records which had been kept for 9,000 years. 
Parts of the Hermetica appeared in the 4th-century Gnostic library found in Nag Hammadi.— another famous tract is the Emerald Tablet of Thoth, which teaches the doctrine "as above, so below". The Hermetica are Egyptian-Greek wisdom texts from the 2nd and 3rd centuries CE, which are mostly presented as dialogues in which a teacher, generally identified as Hermes Trismegistus ("thrice-greatest Hermes"), enlightens a disciple. The texts form the basis of Hermeticism. They discuss the divine, the cosmos, mind, and nature. Some touch upon alchemy, astrology, and related concepts. Orders-Hermetic Order of the Golden Dawn - Hermetic Brotherhood of Luxor -Hermetic Brotherhood of Light -Ordo Templi Orientis (Aleister Crowley)
Through the perfect union of the two forces, as an example of the Gender Principle with Adam and Eve in the waters of sex with chastity, the pillar of the hermai is perfected and made into the image of God through the hierogamic union of the inner Christos-Sophia. This is represented in Alchemy of unified polarities. In this term of hermaphrodite we see Mercury (Hermes) uniting with the goddess of love. Her name is Venus or Aphrodite. When Hermes and Aphrodite unite they form Hermaphrodite, the perfect balance of unified male and female principle. A hermaphrodite really, truly has nothing to do with what people currently think that it is. The mystical understanding of a hermaphrodite, is the etymology of the word comes from the union between Mercury and Venus (hermes-aphrodite), and is the hierogamic union of a god and goddess, a perfected being, the perfect balance and union between masculine and feminine, united as one. When we enter the sexual act, we mimic that process in varying degrees of Consciousness. We enter into a sacred temple, the union of polarities to form a unity. Because we are ignorant and subjected to the Sexual Misery programming on the earth, but we corrupt it with our lust, jealousy, pride, arrogance, with animal desire - the Houses of Ego. When we think with the Negative Ego mind and allow the Imposter Spirit to dwell inside of us, we do not have a clean, pure temple; our inner temple has been made into a brothel.