Be careful what substances you decide to create endogenously from the third eye. Some of these can kill you like opiates.
For this spell, begin research into the substance you want the third eye to produce. Meditate and imagine the pineal gland producing the substance. You can visualize the molecule, crystals (For DMT) mushroom spores (For Psilocybin) or anything else that represents the substance you want to be produced inside of your own body.
This is meant for microdosing or enhancing your spirituality and not getting high off of your own supply. You must also keep in mind that magically putting drugs in your bloodstream can cause you to fail a drug test.
No, I meant the latter way you said where the third eye creates new matter inside of your brain. If you know the chemical structure it can be simplified enough to the point you can think it into existence.
Look I don’t wanna come off as a reddit atheist disrespecting your beliefs, but our minds physically cannot provide the conditions let alone produce and withstand the energy required for matter creation. E=mc^2. In order to inverse this equation, the kinetic energy and resting energy of a massive particle would need to be at least double its resting energy. The only way to achieve such a feat would be to reach near relativistic speeds only capable in a vacuum where photons collide. That would require the manipulation of our energy outputs expended by our brains, the careful direction of photons through supercharged conductors like gold, higher energy requirements than what we’ve been able to achieve with particle colliders creating electron-positron pairs for proton and neutron creation for the creation of these compounds, and some method of dealing with the newly created antimatter. How exactly does the pineal gland accomplish this?
For those who do not believe the third eye can inject drugs directly into the bloodstream, the third eye can still manifest things like a good drug dealer or finding mushrooms in the woods.
For the scientific thing that’s how things happen in a secular way. This can only be from the spiritual side.