How to remap Caps Lock to a specific key?

By default I have the following key mapping:

$ xmodmap -pke
...
keycode  49 = oe OE oe OE leftdoublequotemark rightdoublequotemark leftdoublequotemark
...
keycode  66 = Caps_Lock NoSymbol Caps_Lock
...

I assigned Ctlr to keycode 66 by doing $ setxkbmap -option "ctrl:nocaps" Now I'd like to assign Caps Lock to keycode 49. I did:

$ printf "keycode  49 = Caps_Lock NoSymbol Caps_Lock" > ~/.Xmodmap
$ xmodmap ~/.Xmodmap

The result was that pressing keycode 49 activates Caps Lock but pressing it again doesn't deactivate Caps Lock... How could I toggle Caps Lock by pressing keycode 49?