Aside from viewing the universe as power, which has numerous ramifications that will be addressed more explicitly later, another central idea in the metaphysical postulations of 'tantra' is the equation of the microcosm with the macrocosm.
The maxim (which he quotes in nearly all of his works and sometimes several times in the same work) that seems to drive his assertions is derived from the Vishvara Tantra which states:
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"'What is here is elsewhere; what is not here is nowhere' (Yadihasti tadanyatra vannehasti natatkvacit)."

 
These constructions emphasize the correlation between the physical human form and the world from which these texts arose, both mythological and topographic.
The cosmic axis of the universe, Mt. Meru, is equated with the spinal column of the human body, while the various mythologically constructed lokas (worlds) are said to reside in the cakras.
As a representative characterization (many similar statements can be found throughout his work), allow me to quote from the preface of the Mahanirvana Tantra.

"The nadi are the rivers. The seven substances of the body are the seven islands. Sweat, tears, and the like are the oceans. Fire exists in the Muladhara, sushumna, navel, and elsewhere. As the worlds are supported by the pravahana and the other vayu ('airs'), so is the body supported by the ten vayu prana etc. There is the same akasha (ether) in both."

These correspondences, while playing a fundamental role in the majority of his works, seem most central to The Serpent Power, a work exploring the inner workings of Kundalini Yoga, which additionally translates the Sat-cakra-nirupana and the Paduka-pancaka. The Sat-cakra-nirupana especially takes as its object of exposition the correspondences between the microcosm and macrocosm.