I have tried any and all combinations of the URxvt.font but it just isn't working. This is how my .Xresources file looks like:
! URxvt
URxvt.foreground: white
URxvt.font: xft:monospace:size=10.5
URxvt.letterSpace: -1
URxvt.depth: 32
URxvt.background: [90]#000000
URxvt.scrollBar: false
! Xft
Xft.autohint: 0
Xft.lcdfilter: lcddefault
Xft.hintstyle: hintslight
Xft.hinting: 1
Xft.antialias: 1
Xft.rgba: rgb
Xft.dpi: 120
However it doesn't care if I set size to 10.5 or 100.5, the size won't change. Even xrdb -query shows it's set to size=100.5 but all the text would be very small. It only happens with the monospace font (which is mapped to Inconsolata). Any other font gets resized just fine. pixelsize works, too, but I need to use size because it lets the font scale according to Xft.dpi.