Setup Assistant Cannot Find Time Machine

I have purchased a new iMac and i am attempting to transfer over my data using a time machine back up. However, during the new mac set up process, when I indicate that I want to transfer my data via time machine the new imac has been unable to locate the hdd containing my time machine. It has been searching for over an hour at this point.

The old iMac is an ancient G5 running Leopard.

Thoughts?

 

An ethernet connection is my last resort. I actually don't have physical access to either mac. I am assisting a relative with this process via the phone with a little FaceTime mixed in. Walking them through transferring the data via ethernet might be difficult. I'd really like to get this Time Machine backup to work.