How do I create a custom resolution for an external monitor?

Question

I currently trying to add the resolution 1216x676 for my external monitor which is connected via HDMI-1. I'm following the guide found at http://shanereustle.com/blog/force-screen-resolutions-on-ubuntu.html.

Here are the commands I've tried:

$cvt 1216 676 60

output is

# 1216x676 59.87 Hz (CVT) hsync: 42.09 kHz; pclk: 66.00 MHz
Modeline "1216x676_60.00"   66.00  1216 1272 1392 1568  676 679 689 703 -hsync +vsync

Then I try $xrandr --newmode "1216x676_60.00" 66.00 1216 1272 1392 1568 676 679 689 703 -hsync +vsync

The output for this command is:

X Error of failed request:  BadName (named color or font does not exist)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  16 (RRCreateMode)
  Serial number of failed request:  37
  Current serial number in output stream:  37

Any help would be appreciated.