Actually, mescaline is
mentioned.
Once NEO looks up in the mirror he sees himself double-sided for the first time, his false ego dissolves and his actual self remains in the mirror. Wondering who did but it's only his self that bends...
Once he touches the mirror with his finger...
See the upper top of the pyramid house in the mirror? It symbolizes divinity and while he senses the top, all that happens is him going back to his very pure self, becoming completely transparant.
In his cocoon he gets a shot of all the energy sucking plugs that have been attached to his physique since his birth. Just a full break-through experience, which reminds a lot of DMT due to the rapid onset. However, every psychedelic corresponds.
As Morpheus said about dying: "The body can't live without the mind". The mind is always present, but physically one merely exists outside the matrix.
Now that's the point of mescaline, as well as the green electricity. If you consume lots of cactus you'll feel what physical presence is, and it's much more a dream than acid. I actually consider LSD as quite bordered when it comes to the deep inner perspective and awareness of being in your body.
People have lost physical susceptibility completely, and are now desperately crawling in a world to satisfy their minds, in vain. That's the whole, as NEO walks outside the cellphone, he's aware of his sensations from tone to head. Now he exists. The mind is just the operator.