Dear Karl and Rick,
I no longer believe it wise to take mind altering substances to try to shift one's consciousness onto the/a plane of truth. This is because of a new understanding I have come to. I now believe that we already - all of us - exist on the singular plane of truth (which incorporates all other perceived planes) but that we do not ordinarily experience this as it is typically veiled from us in our day to day lives.
I personally make daily efforts, through spiritual practices, to try to 'lift the veil' and remember that I abide in the one-and-only plane of truth that is being-consciousness-bliss (sat-cit-ananda in Vedanta terms). I meditate with this effect in mind. I pray to God with this effect in mind e.g. 'Oh Lord. Lead us from the unreal to the real'. I practice work, devotion and thought with this effect in mind.
I guess it might be alright to use a mind altering substance to reach the truth, so long as the user's intent/belief is that the drug is going to be efficacious by temporarily lifting the veil of illusion to reveal the real state of affairs beneath. However, I see dangerous pitfalls in the 'drug taking' approach to reaching the truth:
The whole idea of putting a drug into the body to change the mind is a concept that gives the drug and the body primary importance over the mind. Change the body with a drug and the 'inner' mind will follow. That is to say that drug-taking is seen as a thoroughly 'matter over mind' activity. A correct outlook however, as sages from all traditions have timelessly told, is that matter is subordinate to mind. When a person cares to put any effort into acknowledging the world, they find that it is consciousness that trumps matter every time. It is our consciousness which provides the light by which we see the world.
The whole process of drug taking is one of ego-centred escapism. This is clear from the terminology used. When one takes a drug one goes on 'a trip'. When one returns from the trip one finds oneself in the mundane life that has persisted all along. This is the 'come down'. With such an outlook no permanent underlying change of perception has taken place. No veil has been lifted. Reality is what it has always been (and quite depressingly so). The conclusion of the drug-taker must therefore be that the misery of life can only be endured through distraction from the ugly truth and further bouts of escapist drug taking. Whoopee!
That being said, I'm wondering if either of you would like to buy a small quantity of psychotropic drugs which I no longer have use for. I can give you a good price.
Take care out there. See you soon.
Paul