Grimrock

i have no idea what to do as soon as i enter this puzzle. There's three pits in a line, and a pressure plate. Standing on the pressure plate produces three clicks, then a teleporter flashes up. I can throw things into the teleporter, but nothing changes! Items thrown into this appearing teleporter that are less than or equal to the weight of a torch (1.2 kgs) appear behind the grill next to me. Items heavier than this go somewhere else (I swear i saw one appear near the other teleporter i can just see in the corner of my eye, but that hasn't happened again.)

I've tried throwing items of every different weight i have, and then tried throwing everything i have through, and nothing happens. Could someone please point out where i'm going wrong!

help would be much appreciated.

(the time bit seems obvious, so what's the tide? I presumed it was weight, but is it water?)

Baisically you're doing everythin right, but

Throw by right clicking a rock or knife out of someone's hand. it goes further.

thanks guys.