The units for the Poynting Vector -- in SI Derived Units -- are expressed as watts/meter^2. Or, expressed in SI Basic Units: kg/s^3 (kilograms divided by seconds cubed). This is extremely revealing.
On one side of the equation you have Electric cross Magnetic, and on the other side you have the units of mass! The Poynting Vector is a Grand Unification Theory!
To simplify its use in calculations, examples of the Poynting Vector usually appear in reference to cylindrical spaces -- not spherical spaces. [If you are aware of a company that makes resonant harmonic cavities -- especially, spherical resonant harmonic cavities -- please E-mail John Nordberg. I would like to obtain one for experiments.]
There is a reference to "electromagnetic mass" on page 56 of Atomic Physics by Max Born (Dover Publications, Inc. ISBN 0-486-65984-4). This theory was developed by such renown physicists as: J. J. Thomson, 1892; Heaviside and Searle, 1885; Kaufman, 1906; Abraham, 1903; and Hasenohrl, 1906. I have not been able to find out more about their research. If you know of their research, please E-Mail me.
Readers may be interested to know that what stopped development on this promising theory was Einstein's Relativity. Another weakness of this early theory was, Why doesn't the electromagnetic field disperse? What "holds" it together? In hindsight the answer is gravity. For example, photons pivot around the gravitational field:
This is a vivid example of the Poynting Vector in action! (The electric field, E is represented by blue arrows in this example. The magnetic field, B is represented by magenta arrows in this example. The gravitational field G -- or Poynting Vector, S depending on how you interpret what's happening -- is represented by the green arrows in this example.)