how to find the inductance of a cupper rod?

http://www.consultrsr.com/resources/eis/induct5.htm

I wonder, how you want to calculate the inductance without specifying a return path?

Maybe calculation is for case of electrostatic discharge through rod?

i assume the return path is in infinity , is n't that a valid assumption

If you apply transmission line equations, infinity return path results in infinite inductance.

asume i want to find the inductance of only one rod how can i determine the return path?/

In my opinion, the inductance isn't defined without a return path.

I am confused. Following this discussion I am thinking how to remove from the lab all the inductance meters that I have, because I don’t have a return path for them.
From where I can get (or to buy) a return path for an inductance?….any ideas?