How to boot from ISO without USB stick or DVD on Mac OS X 10.4.11 Tiger
It's technically possible if you have your hard drive partitioned with the ISO on said partition (and made bootable of course). Otherwise, you'll need to use a USB or disk in order to boot it. If you go with the first option, you can use either Disk Utility or Terminal. This should help if you're using Terminal: http://osxdaily.com/2012/03/13/burn-an-iso-image-from-the-command-line/