The Tao of Physics (full title: The Tao of Physics: An Exploration of the Parallels Between Modern Physics and Eastern Mysticism) was a 1975 book by physicist Fritjof Capra, published by Shambhala Publications of Berkeley, California. It was a bestseller in the United States, and has been published in 43 editions in 23 languages. The fourth edition in English was published in 2000.

The following quote from 'The Tao of Physics' summarizes Capra's motivation for writing this book.

"Physicists do not need mysticism, and Mystics do not need Physics, but humanity needs both." - Fritjof Capra

The book grew out of an inspirational moment Capra had while under the influence of psychedelics. Capra later discussed his ideas with Werner Heisenberg in 1972, as he mentioned in the following interview excerpt:

    :"I had several discussions with (Heisenberg).  I lived in England then
     (circa 1972), and visited him several times in Munich and showed him the
     whole manuscript chapter by chapter. He was very interested and very open,
     and he told me something that I think is not known publicly because he
     never published it.  He said that he was well aware of these parallels.
     While he was working on Quantum Theory he went to India to lecture and
     was a guest of Tagore.  He talked a lot with Tagore about Indian
     philosophy. Heisenberg told me that these talks had helped him a lot with
     his work in physics, because they showed him that all these new ideas in
     quantum physics were in fact not all that crazy.  He realized there was,
     in fact, a whole culture that subscribed to very similar ideas.
     Heisenberg said that this was a great help for him.  Niels Bohr had a
     similar experience when he went to China." 

- Fritjof Capra, quoted in the book 'Holographic Paradigm' by Renee Weber (1985, pg 217)

In fact, Niels Bohr was inspired to adopt the yin yang symbol on his family crest as a result of his contact with China and Chinese thought. Given this, and Heisenberg's own philosophical leanings, Capra's attempt to relate physics and eastern philosophy can be seen to be not unheard of at the time he authored 'The Tao of Physics'.