I guess I run counter to the majority here, but I tried a helmet mounted mirror first before going with a Take A Look mirror on my glasses. Since I wear prescription eyeglasses and identical sunglasses, it is easy for me to mount and dismount the mirror to either pair of glasses. The weight hasn't been an issue for me, and I like the view I have with the mirror on my glasses.

I take off the mirror when I get to work, and stow it in my trunk bag.