From all of the information on this site, that possibility certainly exists. Maybe even the third glass, too. The idea is that some absorption into your body will occur with each cup, even if they are vomited. The collective amount of the multiple cups should result in an adequate amount being absorbed to cause CTB. In order to minimize the potential of vomiting, this is why a protocol was developed, of which anti-emetics are a part. If you haven't yet, read the entire SN Megathread, and even do some searching for anything else you can find on SN.