Rice Cereal in bottles?

Hello. My son is almost 3 months old and is eating anywhere from 2 to 5 oz every 2 to 3 hours. He will sleep from about 11 pm to anywhere between 2 and 4 in the morning ready to eat again. I also would like to know how much rice you would put in a 4 oz bottle. Im going to talk to his pedatrition next week at his appointment and I WILL NOT start anything until, this is all out of curiousity