On a numerological basis twelve- or sixteen-year-old girls are preferred. Only when none can be found does Tsongkhapa recommend the use of a twenty-year-old. There is also a table of correspondences between the various ages and the elements and senses: an 11-year-old represents the air, a 12-year-old fire, a 13-year-old water, a 14-year-old earth, a15-year-old sound, a 16-year-old the sense of touch, a 17-year-old taste, an 18-year-old shape or form, and a 20-year-old the sense of smell (Naropa, 1994, p. 189).
The rituals should not be performed with women older than this, as they absorb the “occult forces” of the guru. The dangers associated with older mudras are a topic discussed at length. A famous tantric commentator describes 21- to 30-year-olds as “goddesses of wrath” and gives them the following names: The Blackest, the Fattest, the Greedy, the Most Arrogant, the Stringent, the Flashing, the Grudging, the Iron Chain, and the Terrible Eye. 31- to 38-year-olds are considered to be manifestations of malignant spirits and 39- to 46-year-olds as “unlimited manifestations of the demons”. They are called Dog Snout, Sucking Gob, Jackal Face, Tiger Gullet, Garuda Mug, Owl Features, Vulture’s Beak, Pecking Crow (Naropa, 1994, p. 189)