moodboard: "Tantra of the Tachikawa Ryu : secret sex teachings of the Buddha" (John Stevens 2010). Image: "Pleasure Competition in the Four Seasons" (Chôbunsai Eishi. Circa 18th Centaury)

"Sutra of Secret Bliss 

The text it's self is a short tantra (exposition). It reads as follows: "Sexual intercourse between a man and a woman is the supreme buddha activity. Sex is the source of intense pleasure, the root of creation, necessary for every living being, and a natural act of regeneration. To be united as a man and woman is to united with Buddha." The sound A represents the Womb Realm (Garbhakosa-dhatu; Taizo-kai/胎蔵界), Mother (Yin/in), great compassion, and the red lotus. The sound UN (hūṃ) represents the Diamond (vajra) Realm (Vajradhatu); Kongo-kai/金剛界), father (yang/yo), Wisdom, and the white Stupa. A/Un (the alpha and omega) represents is female/male (non-duality, paradox), yin/yang, ocean/mountain, mercy/charity, emptiness/form. The red seed from the female and the white seed from the male bring human beings into existence. The unity and integration of A/Un creates and sustains the universe. This is the truth, not falsehood. 

Prior to performing these rites, the man and woman take these vows: 

1) We trust in the teachings of the Tachikawa-ryu. 

2) We vow to cooperate and come together in mutual accord in the body and mind at all times. 

3) We vow to perform these rites carefully under strict supervision by a master of Tachikawa-ryu. 

4) We vow to try not to argue or fight. 

5) We vow to try and avoid competing, making unconstructive criticisms, or blame each other. 

6) We vow to try not to over indulge in food or drink. 

The Buddha couple should bathe together in a curative hot spring without physical contact. The couple must be in perfect accord in body, mind, and speech. The couple must be in bright, positive mood, free of gloom, despair, or unhappiness. The man is venerated as Fudo myo-O (Acala); the woman is venerated and embodies Aizen myo-O/愛染明王 (Rāgarāja). The holy couple faces each other and they make the three prostrations (sanrai). 

Reciting:  Male: "I aspire to enter the Womb realm." 

Female: "I aspire to receive the Diamond (vajra) realm."

The room must be spotless and absolutely clean, well secluded, with a small altar. The secret buddha image is kept veiled, not to be uncovered until after the rites are performed. Kuden (secret oral teaching), the instructions regarding The Buddha image are only to transmitted orally and never written down. Fresh flowers are placed on the altar, together with appropriate seasonal offerings from the mountains and the sea. Kindle fragrant incense. Light the room with five candles. (The candles are the five colors of the elements and are placed in the appropriate direction: fire-red, south; water-black, north; wood-green/blue, east; earth-yellow, south; void-white, west) The Buddha image is one's own body. Therefore, the man and woman shed their robes in the corner (southwest) and face each other completely naked and adorned. The Rites are to begin at midnight. The man crosses his legs in the full lotus position and the woman sits on the top of the man and lets his jeweled jade stem enter her mysterious gate. (This posture reacts the position of many esoteric deities and their consorts, in particular that of Shiva and Shakti). 

During the sexual congress of the two roots of existence (A/Un), the breath should be harmonized in an A (inhale) and Un (exhale) rhythm. The man should keep his vajra pressed against the woman's womb as they meditate together, blending the male/female components of the five elements (godai): earth, water, fire, wood, and air/void. If done properly, this blending of the elements will form a five-colored rainbow: yellow, blue, red, green, and white. The mother/father buddha posture is best, but other postures and mantra are allowed. (goku-I kuden ari: secret oral instructions and essential teachings are given but unknown at this time) However, at the break of dawn when the rooster crows, The Buddha couple should be in the mother/father posture. At that time, The Buddha couple should come to a mutual instant of universal bliss; that is the moment of universal truth, a state of pure ecstasy, an unobstructed integration of emptiness and form. This is the realm of Dianichi Nyorai (Vairocana), the Cosmic Buddha where myriad elements exist in perfect equilibrium." 

From:   "Tantra of the Tachikawa Ryu : Secret sex teachings of the Buddha (2010)"