I just looked up the Kornfield vagina thing and there's a bit of context that I think should be brought out, namely that it is part of a discussion of the chakras:
The second chakra, just above, is in the area of the genitals. Its energy usually opens us up to aspects of sexuality, reproduction, and generativity. When the energy of sexual release opens in this center, we may be flooded with sexual images and sensations for hours, days, or even weeks. For some, this may be pleasurable. For others, who may have issues of sexual abuse or painful sexual histories, it can require a confrontation with the fearful and destructive side of those energies.
The second chakra can produce visions of every kind of sexual encounter along with tremendous waves of lust and rapture. For one woman in a recent retreat, the opening of this chakra began with hours of powerful erotic and orgasmic vibrations. Then she saw visions of the copulation of humans and animals in every realm. It looked to her as if the trees were copulating with the sky, and when she sat in meditation she felt as if the entire world was being poured into and out of her vagina in an enormous sexual act. Initially this was overwhelming, but over some days she gradually relaxed and allowed the process to open to a sensitive and calm state filled with an exquisite sense of joining with all things. This chakra connects us with the boundless reproductive capacities of the world.
His section on the chakras begins as follows:
We may also encounter great changes through the opening of the energy centers in the body traditionally called chakras. This process does not happen for everyone, and it is in no way necessary for a full spiritual life. Indeed, openings of the energy body and chakras occur simply because a person has been blocked and held in these areas, and the experience arises as our inner energy tries to move and free itself in the body.
and it ends in this way:
These energetic processes can take place in a period of hours or weeks or months, and for many students they are a process that goes on for years. They are all a part of an opening and purification that is the natural product of deep spiritual practice.
Further, the section on chakras is part of chapter 9, "The Spiritual Roller Coaster: Kundalini And Other Side Effects", which begins as follows:
The dazzling effect of lights and visions, the powerful releases of rapture and energy are a wonderful sign of the breakdown of the old structures of our being, body, and mind. However, they do not in themselves produce wisdom.
There is not only nothingness because there is always, and always can manifest. - Thinley Norbu Rinpoche