Dual-booting the Mer-based Nemo Mobile on Nokia N950
Editor: Andrew Olmsted
Instructions for dual-booting Nemo Mobile on the N950 are available at the Mer Project wiki. The process involves extracting and flashing a specially modified file onto the device. The process is reversable and doesn't seem like it should affect your Harmattan install (although backing up is obviously recommended before you start the process). It is simple enough really. Turn the phone on like normal, be prompted with a few warnings and a standby screen featuring green text. Now, to boot into Harmattan, press the Volume Up button, to boot the Alternate OS, press the Volume Down button.
Read more (wiki.merproject.org)
Read more (mynokiablog.com)