A study published in 1951 found both Mescaline and Trichocereine in T. terscheckii.
Typically they found a 5:1 ratio of trichocereine to mescaline and their results ranged from 0.25% to 1.2% whole plant alkaloid values. However in at least some of the plants with higher values they noted that mescaline was absent.
Trout published a reference to the study and the basic details in TN3B San Pedro:
RETI & CASTRILLON 1951
What is interesting is that they broke the plants down to different parts including what appears to be the inner cores, the outer green tissue and the part in between.
In their reporting they found that the inner core contained 45% of the total alkaloid, the reported that the outer part, the green skin, contained 29% of the total alkaloid, leaving 26% for the remaining tissue, presumably found between the core and the skin.
Note that only 1/3 of total alkaloid was found in the outer skin, however consider that this outer skin is thin and light, so it has a much higher concentration of alkaloids on a weight for weight basis than the rest of the plant does, despite having less alkaloid over all.
These results indicate that there is a strong possibility that other close relatives of this plant have similar values and concentrations.
for example, say that an outer skin of another species has a value of 1% alkaloid by dry weight, the rest of the plant could contain 2X more alkaloid than this, but since it has more mass the value would be far lower than 1%.
Also note that in this case alkaloids were found in vascular tissues, this suggests that either diffusion or translocation occurs. In tasting older and established roots it is also clear that trichocereus roots contain some alkaloid making them quite bitter.
One thing to take away from this is that by keeping the outer skin and throwing away the core a person may be discarding as much as 2/3 of the total alkaloids.
Note as well that in regards to T pachanoi, Cruz Sanchez 1948 found about 5% mescaline by dry weight in the outer skin/bark, though it is assumed that he would have had 3,4-DMPEA in his results as well as that it crystallizes with mescaline and cannot be separated without chromatography or ion exchange resin. To consider the results of Sanchez note that the 5% was likely to be 1/2 to 1/3 of the total alkaloid in the plant, but since the outer green skin is much lighter in weight then the total values for the whole plant were clearly less than 5%, perhaps closer to 1-2%.
The pachanot clone or PC has been tested and found to have about 0.15% mescaline by dry weight, the outer skin may be around 4-5X stronger be weight, despite having only a portion of the alkaloid, making the value of outer skin near 0.6% or so. This implies that 1000 grams of dried whole plant of PC would have about 1.5 grams mescaline, in extraction it is unlikely that all of this would be recovered. in outer tissue the value should be higher, 1000 grams of outer skin of PC should contain up to 6 grams mescaline or so, making the minimum dose of the skin 50-100 grams, this is rather consistent with reports of the activity of the PC clone.
note that strong clones can be fully active when doses of 10-20grams (of whole dried plant) is taken.