I would recommend 10-15 seeds, assuming you have the allegedly potent "Hawaiian" strain. I'd be cautious about going anywhere past 20 seeds due to the side effects. Keep in mind these seeds lose potency rather quickly.
The first time, I took 7 seeds in a smoothie -- made me nauseous as hell. Had a dark trip where I thought about fading into oblivion a mere blip in society. Then I threw up and it instantly turned euphoric. I thought about my 74 Super Beetle and got red, hexagonal, machine-scape CEVs consisting of my car's gears, drivetrain, etc.
Another time, I held about 11 seeds in my mouth for a good 45 minutes before spitting it out. The nausea was negligible. On my way to the book store, the cracks in the road were dancing.
Yet another time, I held 13 seeds in my mouth for about 20 minutes before swallowing. Nausea was overbearing, but I beat it back with marijuana, after which the trip turned quite pleasant with euphoric tactile sensations. As I took it pretty late, I had difficulty sleeping. I had to drive later that morning and my sense of space was still slightly distorted. /!\
The last time, I held about 13 seeds in my mouth for a good hour before spitting. It barely had any effects. This is most likely due to the fact that the seeds were several months old by this point. My friend, who was also taking the seeds, performed a makeshift cold water extraction by spitting chewed-up seeds (about 15) into a water bottle, shaking it periodically for about a half hour, and then drinking the water using a napkin as a filter. Reportedly, he tripped fine without considerable nausea.
