Many critics and cultural watchdogs contend that the power of pornography stems from its portrayal of deviant acts, and that objectionable material consequently represents not only the most tawdry and disreputable interests, but also the most dangerous. But as dozens of famous court battles have countered, both arguments tend to ring false under even a modicum of scrutiny. Pornography does not depict transgression, exactly; it depicts the illusion of transgression, an essential component of fantasy. Forbidden Erotica, a nearly 500-page collection of dirty pictures taken from around the late 1800s to the early 1900s, makes this illusion literally more explicit. The book's hundreds of images capture the act of coitus in nearly all its forms, offering a hardcore, gynecological glimpse into the past that may surprise not only modern-day pornographers and self-appointed sexual adventurers, but also those finger-pointers who view porn as a contemporary phenomenon. Forbidden Erotica demonstrates that, from the Kama Sutra to today's multibillion-dollar adult industry, anything that can be thought of (given the physical limitations of the human body) can and has been done. That something so essential to humankind can still be considered shocking comes from confusing illusion with reality and equating vicarious transgressions with the real thing. But while you can sometimes halt the distribution of pornographic materials, you can't halt the acts themselves, so pornography will always exist in some form. There's plenty of it on display in Forbidden Erotica, and the smut can be fascinating from a historical vantage, especially compared to today's artificially inflated physical ideals. These pictures redefine the concept of "amateur," while the quaint handlebar mustaches, old hairstyles, and the odd glimpse of period garb will forever cast shadows on the spurious innocence generally projected on the past. The old line on the subjectivity of porn goes "I know it when I see it," and most everyone will see it here. But the book does offer a history lesson, however scant, making Forbidden Erotica a valuable portrait of another invisible time. Or at least the only coffee-table book you'll ever hide under your mattress.