As long as you can see the pillow in one?

Mainly seen in the eyes. The rest varies from person to person. Some laugh all the time, some are exaggerated and some are chilling out on the other hand totally aggressive. After 2 hours of fun is over.

yes, you won't be able to see clearly once you have smoked pot. however, the second time you do it, it might not be that blurry. i like your basis of seeing pillow in one. i have not heard this as the basis for measuring the depth and weight of the smoked pot. of course, no one notices it because sight and experience are very subjective and personal.