The late great psychonaut and author DM Turner has written a book about Salvia, and in it details his accounts of combining Salvia and DMT together:
http://www.erowid.org/li...ine/salvinorin/j9.shtml
After returning from this DMT journey I got the idea of smoking Salvinorin
and DMT simultaneously. At the time I did not think to consult with either
the Salvia entity or the DMT entity, and proceeded with my planned experiment. I smoked 30 mg. of DMT in three tokes, followed immediately by 650 mcg. of Salvinorin that I had preloaded in a separate pipe.
The effects were felt almost immediately. The first thing I noticed was a
grid of crosshatch patterns. I had perceived something similar when using
2C-B with mushrooms, which I believed to be the result of using two
psychedelics that were not compatible with each other. However, in this
case the patterns were defined to a much sharper degree, and it seemed
apparent that these two substances affect consciousness in differing ways
that are not synchronistic when used together. Both the Salvia and DMT
entities seemed to have been taken entirely off guard and had not been
expecting this confrontation. These entities seemingly paid no attention
to me as their attention was entirely fixed on each other. It soon became
apparent that the two were going to battle, vying to determine who would
have control of my consciousness.
It was like a scene of two Gods battling in a mythological tale. At first
it seemed that DMT, with its ability to manifest in spectacular forms
displaying its might, power, and ferociousness, would tower up above the
Salvia entity and overpower it. But the Salvia entity moves very fast, is
extremely maneuverable, and has a silent, stealthy force that will not be
denied. Soon the Salvia entity was running circles around, and had
interpenetrated the DMT. It was not a pretty scene to watch, but Salvia
took the upper hand.
The visions I was seeing while watching this battle were severely
distorted. smushed, reversed, and turned sideways. All the favorite
creatures of DMT Elf land were put together with the wrong body pans, or
body parts in the wrong places. Their normally gaudy outfits had been
turned into white and brown plaid shins, and they were wearing brown
leather shoes and carrying brown briefcases, Millions of these miserable
little creatures were frantically running around as door-to- door
salesmen. They were moving perpendicular to everything else on she surface
of their planet, as though they were obeying a gravitational force that
was at a 90 degree angle from everything in their surroundings.
By the end it seemed that DMT was unhappy and had lost face by being
unseated, possibly for the first time. The Salvia entity seemed reasonably comfortable in her ability to deal with DMT. Although she seemed glad that the battle was over, and still very surprised that I had introduced to her something that actually wanted to overpower her, and had made a significant attempt.
Fortunately, neither of these entities seemed extremely upset with me the
next time I confronted them. I've recently had some experiences where
these two seemed to be working together to make changes in my psyche
(although I had used them on separate occasions.) However, I will probably
never combine these entheogens again, unless I get a clear message from
both of them that this is desired. I also have not used Salvinorin with
mushrooms since psilocybin is very closely related to DMT.