(CNN)"The private sanctuary where you sink into a soothing bubble bath and the pretty little powder room in which your guests tidy up before dinner may seem like simple spaces.
Bathing beauties: Step into the world's most luxurious bathrooms
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But looks, as the saying goes, can be deceiving," says Barbara Sallick, senior vice president of design at bathroom company Waterworks, on her quest for the perfect bath.
It's a journey that's led her and her husband Robert, co-founders of Waterworks, to study the bathing habits of ancient civilizations for inspiration.
"Going back to antiquity, we started with the Egyptians, whose obsession with cleanliness was such that they discriminated against cultures whose members didn't follow their own bathing customs," says Sallick in the introduction to her new book, "The Perfect Bath."
"The idea of the bath as a font of relaxation, reflection, and restoration, developed by the ancients, is one that has never been improved upon -- all we can do is translate that timeless concept into a personal reflection of contemporary life," she says.
Sallick's book features some of the world's most beautiful bathrooms, from the simple to the extravagant, to show how one of the most private of spaces can be transformed through the use of color, layering and textures.
And whether large or small, vintage or modern, when it comes to the bathroom, Sallick stresses that the "perfect bath" depends on personal taste.
"The master bath is the only space in your home that is all about you -- a highly personalized domain that, in addition to being part of life's daily routine, serves as a private retreat."