Tantric Art and Meditation

This is an excellent source. It contains the full Goma Fire Meditation, The Lotus Womb Meditation and the Vajra Thunder Meditation. It contains Tantric Buddhist spells, invocations and the associated
mudras and mantras. It isn't sketchy or incomplete either.
My especial interest is the vajra or thunder meditation with the siddham sanskrit mantras and tantric mudras. The ritual meditations described derive from the Japanese Tendai Buddhist tradition, a Tantric form of Mahayana Buddhism dating from the Heian Period in Kyoto.