Don't fall asleep while seated, you'll lose intellect

e7.2 The second cause of minor ritual impurity is loss of intellect (O: meaning the loss of the ability to distinguish, whether through insanity, unconsciousness, sleep, or other. Loss of intellect excludes drowsing and daydreaming, which do not nullify ablution. Among the signs of drowsing is that one can hear the words of those present, even if uncomprehendingly).

Sleep while firmly seated on the ground (A: or any other surface firm enough to prevent a person's breaking wind while seated on it asleep) does not nullify ablution, whether riding mounted, leaning on something which if removed would cause one to fall, or otherwise seated.

If one sleeps when firmly seated and one's rear moves from its place before one awakens, this nullifies one's ablution. But not if:

(1) one's rear moved after or during awakening, or if one is uncertain about whether it happened before awakening or during;

(2) one's arm dropped to the ground while one was firmly seated;

(3) or when one drowses while not firmly seated, hearing but not comprehending, or if one is uncertain as to whether one drowsed or slept, or uncertain as to whether one slept while firmly seated or not firmly seated.