The Thanatos Project was a research effort by Aldus Crick and Roger Price. Crick hypothesized that if Roger was able to stop time while teleporting, in the interval between disappearing and re-appearing, he would arrive "in a time out of time" that they termed limbo.[1]
After repeated failures (at least 458 tries), Roger believed that the only alternative method to reach limbo is by stopping time at the moment before death.[2]