Modern day researchers, spearheaded by people such as myself, have realized that Jonathan Ott's calculations fall short of what most explorers need for a truly visionary experience. Even with a strong harmine/Banisteriopsis caapi dosage, 30-60mg of dmt is not sufficient to produce significant visionary effects in most people. So if fact, a dosage of 30-40mg of dmt is where tryptamine-like effects just begin to occur for most people, and 10-25mg dmt is not really noticeable above the gentle psychoactive effects of the harmine.
Each person is different and for some rare individuals, 30-40mg may be about as much dmt as they wish to take--but most people need at least 60-80mg for sufficient psychoactive effects and even at this dosage, you generally cannot expect a full-blown visionary experience, even when using a strong dose of 4 grams of syrian rue or 100 grams of strong caapi vine. Also, it should be pointed out that going beyond 4 grams of syrian rue (around 200-280mg of harmaline) or 100 grams of strong caapi vine (150--250mg of harmine) can increase the negative effects of these beta-carbolines--which include a feeling of heaviness, pressure in the head, inability to walk properly, more purging and perhaps more of an emphasis on bodily processes.
An oral dosage of 100mg of dmt is where the visionary qualities really begin to occur, for most people say when they are taking 3 grams of syrian rue or 80 grams of strong vine, and in context, 40-60 grams of strong vine is enough to fully mao inhibit most people.
I would say to neophyte explorers to tread carefully, and to slowly increase your dmt dosage in increments: perhaps starting at 60mg, going to 100mg, then 150mg. Some people are going to find 100mg of dmt to be exceedingly strong, and it will perhaps give them an experience they did not feel ready for.
It came to my attention after an embarrassing number of years, that taking freebase crystal DMT orally was not as potent, colourful, or clear as taking the equivalent amount of DMT in a tea that was brewed from the plant. For many years, I couldn't see how there could be a difference, but after doing some comparisons, it was obvious that the tea was much better, and the experiences resulting from the crystalline extract were inferior.
You could take twice or even three times as much DMT crystal as the equivalent in brew, and the experience from the crystal would never be as bright or full as that from the tea. Why could this be?
With extracted dmt, with chemicals used it would appear that some dimensions and qualities of the tryptamine molecules are compromised. Also, there is the factor of isolating the alkaloids from the rest of the plant. For example, there are very few people who say that extracted pure mescaline from the cactus is as potent of full bodied compared to when they take the tea made from the cactus flesh.
When making a tea from the whole plant, you are extracting the essence of the plant intelligence from its very flesh, not just isolating the alkaloids. In the alchemic method "Spagyrics" developed by Paracelsus, often considered the father of modern medicine, the ashes of the plant are commonly burnt and then blended back into an alcohol-extracted tincture. Friends who have experimented with this procedure report that a Spagyric tincture of Ayahuasca is much more potent than a normal tea prepared from the same amount of Ayahuasca vine.