I've had a slightly strange experience with this.
Previous psychedelic experience: LSD 6-7 times in doses between 70ug and 160ug, 2C-B one time at 20mg, MDMA a bunch of time but nothing psychedelic, cannabis occasionally (I have experienced mild color enhancement and some minor CEV on cannabis but obviously nothing even close to LSD)
I have 1.2mg tabs of 25i-NBOMe HCL, and cut one up into small pieces. The first time I tried a dose of ~100ug (+- 50ug assuming the 25i was evenly distributed). I held the blotter against my gums and did not swallow any spit for 15mins. As expected, this was barely threshold, I did notice a slight body buzz and some minor increase in concept recognition (seeing a resemblance to faces in wood grain for example).
The second time I tried ~300ug several weeks later (although I did have an LSD trip 7 days before, but essentially my tolerance was fully down). This time I held the blotter under my tongue with all my saliva for a full 20mins before swallowing. This experience evolved as expected, very mild some "breathing" visuals and a more intense but still quite mild body high. Around 6-7 hours dosing the effects were still very mild but noticeable. At this point, I smoked some weed. I had not smoked for probably around a month so my tolerance is low. Around 10mins after smoking the joint things started kicking off:
I started seeing full blown 3D visuals, mostly words or multi-color geometric structures. I had quite extreme time dilation, and felt like everything was in stop motion, I also felt when walking that I kept being jumped back in time every few seconds (it felt like i was in a recurring loop, always walking forwards but kept being placed back to where I started walking from). It became impossible to act normally and I wasn't really able to talk very coherently despite being mentally quite clear. There were significant audio effects (cars seemed to go past very slowly because of time dilation and the noise of the engines was pitch shifted down into a slow, low drone). At one point the voice of my thoughts became incredibly real, almost like I could really hear it, and I was able to say things in my head in different voices and they sounded extremely life-like. When eating a choc-ice I could hear the crunching very loudly, and also it felt like I was chewing lego blocks or something, it felt like my tongue/teeth etc. were moving very slowly (possibly just the time dilation) and my tongue felt very strange in my mouth (on LSD I've also had a similar but less intense feeling that my tongue is weird in my mouth). Walking back home the perspiration on the road (it was night-time) appeared to me as random words in 3D standing up from the road. I was able to look directly at these 3D visuals and they were not constantly changing like my experiences on LSD. The effects lasted for perhaps 2 hours after smoking the weed before starting to diminish and I was finally able to sleep. This trip was waaay more intense than expected and I was quite anxiety ridden towards the end because I got worried about vasoconstriction (my hands were a little cold and I had a pain in my chest, although this pain is still there for the day afterwards and may just be coincidental since I actually have a recovering shoulder injury for which I am stretching my chest a lot).
I would recommend being cautious with this substance, it looks like a lot of people are jumping in at 1mg+ and I can't even imagine the effects for me if this was combined with cannabis, since on my 300ug dose I smoked the weed after 6-7 hours so should be past the peek but still had such a massive effect. I intend to try 25i again with less than 300ug and no cannabis, but if it looks like the pain in my chest was indeed related to the drug then obviously I will not take it again.
