(Sanskrit, “skillful means”) In Mahayana Buddhism, upaya summarizes the first five paramitas (conscious attitudes), and are therefore “methods” or attitudes of upright action. In Tantric scriptures, upaya refers to sexual transmutation (Tibetan: sbyor-ba).
"The Tibetan Vajrayana school is different; and although its two principal pillars are also “Vision and Action,” [prajna and upaya] it is unquestionable that it places special solemnity on the latter [upaya], and tirelessly struggles to lead its devotees to the Ninth Sphere (sex). It is not irrelevant to assert in this chapter that the aspirants of the Mahayana School truly long for and have an infinite yearning for direct experience of the Illuminating Void [prajna]. We are in no way exaggerating if we state with a certain fervor that disciples of the Vajrayana school labor tenaciously in the “forge of the Cyclops” (sex) [upaya] with the intelligent objective of achieving Innermost realization of the Illuminating Emptiness [prajna]." - Samael Aun Weor, The Mystery of the Golden Blossom