When I last used wireless mice they had two AA batteries and I found it a great relief to go back to a much lighter wired mouse. It hadn't occurred to me that newer battery tech might be lighter. Maybe I should take another look at wireless mice.

EDIT: The Logitech MX Master (a wireless mouse) weighs 145g including battery, and the M500 (corded) weighs 144g. That probably includes the cord, so the in-hand weight might be a little lower, but they're certainly close. Neato.