Walkthrough (part 1):
-Shoot a blue portal on the white surface next to the pedestal switch and an orange portal on a surface somewhere above the entrance door.
-Stand in the portal. Shoot an orange portal on the excursion funnel and a blue portal on the angled surface.
-Press the switch, then go in the funnel. Wait until both you and the cube reach the ceiling.
-Shoot a blue portal on the wall that you used earlier to get an overview of the chamber. Grab the cube and get out of the funnel onto the glass.
-Put the cube back into the funnel. When it is where the two funnels intersect, shoot a blue portal on the ceiling tile. This is the only way to get the cube down to the button without falling into that room yourself.
-This has activated a Minecraft-style "redstone clock", a mechanism that turns on and off automatically. Jump down the glass to the passage with the 2 pairs of lasers. You can now get to the other side easily.

Walkthrough (part 2):
-Shoot a blue portal on the portalable wall on the other side of the lasers. The funnel should now be orange because the cube remains on the button. If it isn't (which may happen), restart the level or commit suicide with the lasers.
-Get into the funnel and get out on the glass again. Jump down to the starting room. Shoot an orange portal next to the pedestal switch.
-Press the switch to receive a new cube.
-Walk through the portal and place the cube on the button.
-Proceed to the Chamberlock.

SPOILER: When at the lasers, it is possible to jump above the lower one and not get hurt by the upper one. Please, if you discovered it, do NOT use this. It is an alternate solution that I can't do anything about. If I used laser fields, they would turn on and off too quickly and trying to walk through would be way too risky.