Holy cow, I wrote a book!
The college professor who carried on a letter exchange with
a kind pensioner who proved that the speed of light could be exceeded
told me of another letter exchange, this time with another
The letter came from England,
and it accompanied some sort of document or artifact that the correspondent
wanted the college professor to look over and return.
The mathematician took the
effort of including a
return envelope with the remark,
"By the commutative law for postage,
I have placed the same amount of postage on the return envelope
as I have on the outgoing envelope."
The professor, however, could not use the return envelope the
the commutative law for postage does not apply to
correspondence between the United States and the United Kingdom
due to events of
slightly more than 200 years ago."