The Indian Buddhist Iconography, Mainly Based on the Sadhanamala and Other Cognate Tantric Texts of Rituals c9.s3.18

c9.s3.18

For the purpose of visualisation it is necessary that the process should be continued for six months and this is done according to the Guhyasamāja always while enjoying all kinds of desired objects If within six months the deity does not show herself the process should be repeated thrice while following the rules of restraint duly prescribed. If the deity is not visualised even after this, it should be forced by the practice of Haṭhayoga. By this Yoga the ascetic most certainly attains the knowledge of the deity.