I haven't heard that there are 26 dimensions, but according to Walter 
Russell, there are 18 dimensions of the relative universe.  
These include:
Dimensions 1, 2 and 3.  Length/Distance, Breadth/Area, Thickness/Volume
Dimension 4.  Time/Duration
Dimension 5.  Sex  (My personal favorite)
Dimensions 6 and 7.  Pressure and Potential
Dimension 8.  Temperature
Dimension 9.  Ionization
Dimension 10.  Crystallization
Dimension 11.  Valence
Dimensions 12 and 13.  Axial Rotation (speed/time) and Orbital Revolution 
(power/time)
Dimension 14.  Mass
Dimension 15.  Color
Dimension 16.  Plane of gyroscopic rotation
Dimension 17.  Ecliptic
Dimension 18.  Tone and Sound
If you want more info on this, you can read "In the Wave Lies the Secret of 
Creation" by Dr. Timothy Binder.  This explains Russell's Cosmogony quite 
well and goes more in-depth into the 18 dimensions.  This is a great book 
with lots of full color diagrams.  I highly recommend it to anyone who really 
wants to learn the fundamentals principles of creation.
As far as what that physicist meant by technically, I have a feeling that 
perhaps he broke some of Russell's dimensions down into sub-dimensions to 
arrive at 26.  Or perhaps he is also referring to "unmanifest" dimensions, 
which may not applicable in a relative universe.  Who knows?  
I find Russell's work to be far more advanced than where science currently 
finds itself.  Even Tesla told him he should put his ideas in a vault for 
1,000 years until mankind was ready for them.    
Warm regards,
Peter