First, the concern that 4 hours per day of sleep being enough:
The idea of "Polyphasic Sleep" is to live healthily on far less sleep than normal.
The theory is that the mind performs most of its recuperative tasks in half a dozen short bursts spread out through a normal, monophasic night's sleep. In polyphase, these bursts are instead spread out in "naps" throughout the day.
The schedule you described is more commonly known as the "Everyman" schedule. The failure rate for most polyphase schedules is about 80%, mostly due to a lack of willpower during the "adaptation period".
The "Everyman" schedule has an adaptation period of about 1 month, during which the schedule has to be followed strictly. One advantage of the Everyman schedule is that naps can be moved about 1 hour forward and backward once one is fully adapted to it (after about 6 months).
* Richard Buckminster Fuller (of geodesic fame) was the first *well-recorded* polyphase. He slept 30 minutes every 6 hours (2 hours a day, the bare minimum). His schedule is known as the "Dymaxion" and I personally recommend not even trying it. He lived on the schedule for about 2 years, with no problems.
* Puredoxyk is the most well-known polyphaser who wrote the first article on the internet about polyphasic sleep. She has a book entitled "Ubersleep". She has been on both the Uberman (20 minutes every 6 hours; totals 2 hours a day) and vanilla Everyman schedules, the latter of which she is still on till today.
* Marc Beneteau
* Steve Pavlina
* Dr Piotr Wozniak recommends "free running sleep", which basically means "sleep for as long and whenever you feel like it", which is more insane than normal polyphase.
Done with the science-y bit.
* Remind him that polyphasic adaptation is not a game. It requires an extraordinary degree of motivation.
* He needs a _good_reason_. Too many people go into it because it sounded cool, and then fail. A pathetic waste of time. It also gives polyphasers a bad name, so I strongly advise NOT to go into polyphase IF YOU DON'T HAVE A GOOD REASON.
* Jobs and education and social interaction do not encourage polyphasic sleep. Especially jobs. Taking a kip twice or thrice in a day is not an idea that bosses in Western countries are yet adapted to (you might get away with it in countries like Spain that practice taking a siesta -- i.e: an hour nap in the middle of the day. N.B: Studies have shown taking a siesta has been shown to be more healthy than normal sleep.).
** The above is a big factor. Buckminster went back to monophase because his business associates "wanted to sleep like normal men". So his "additional waking hours were not productive".
* Most do better when they have someone they know go through it as well.