|N version||1.3 and later|
Method 1 (Easy)
Inside, pick a side (normally left). Of the 3 switches, hit the top left first, then drop down to the bottom right, then go to the bottom left. Hopefully none of the drones will have seen you, then make your way back to the top of the pit. Then walljump out, avoiding the gauss turret.
Hit the switch on the left (or right) side, and then get into the thwump area. There, to be cautious, bait each thwump before you jump into that area.
Jump back out (baiting again), and then get back into the pit area similarily to the beginning, except this time it is much easier; just drop into the door.