Apparently this has been known. Carry on.

I don't know if this is the place to post this, or if enough people run Legacy no OoB to care, but I'll put it here and maybe someone will tell me to move this somewhere more beneficial/acceptable.

In test chamber 4, if you can get the bottom of the pit in view before the cube drops, you can shoot a blue portal right where the cube would land, and the cube would have enough momentum to land onto the button. Sometimes it does go past the button, but if it lands on the button, it saves the hassle of doing it yourself, which I've seen most runners do in their video, so I imagine it saves a few seconds, maybe less, I don't do this enough to know for sure.

Posting this so that perhaps someone would care, thus making it worth sharing. If not that's okay too. Haven't gotten a video of it by the time this post comes out, I'll probably attach it to this post when I get one.