Tantric Imagery
Here's a larger view of the central image in the opening page. The visual union of these two deities (with their multiple arms holding various implements) symbolizes the union of Wisdom (prajna, which is grammatically feminine) with Skill in Means (upaya, which is grammatically masculine).
Buddhahood is described as the perfect attainment and mastery of these two qualities--Wisdom informs one of the right thing to do, and Skill in Means allows one to transmit this wisdom in the most effective way.
Note the garlands of skulls hanging from the figures' waists--a symbol of the commitment needed to walk this path. Note too that it's difficult to discern where one torso ends and another begins--showing how these qualities interpenetrate each other in everyday experience.
Down below are larger views of the border images found on the opening page (the image at left is at the top of the picture, and the others proceed clockwise).
Such explicit imagery was a radical way to affirm ultimate unity through union of polar opposites. Although this image may have been produced for the tourist trade, the original images were often used as meditation tools by celibate Buddhist monks. This is one more piece of evidence for understanding these pictures as symbols.
Copyright James G. Lochtefeld 2006