The type of battery makes a big difference.
I've just tried connecting a Sony sld1236vl directly to a few batteries.
It's rated 80 mw cw at 130 ma 2.5 v. Threshold is less than 50 ma.
No way I want to push it to it's max 250 mw (pulsed mode)
A couple LR44 button cells get it above threshold...