Deepweed makes adepts and magicians astrally perceive (even if the adepts don't have the power). The thing you're thinking of is Tempo, which caused a massive drug war, along with a whole host of other issues as it opened normal metahumans up to astral tampering, as they were simultaneously dual-natured and high as fuck. It was considered a crisis, and there's basically no Tempo available anymore. Not to mention, as a BAD (Bioengineered Awakened Drug) it probably had heinous side-effects, and was described to be super addictive, both physiologically and psychologically, with users quickly gaining a resistance to it and needing more and more to feel the effects.
As training to skill level 1 takes only one day, you could try and argue that if you were on Tempo for like 12 hours, you could buy a skill point... But you'd need to be training that whole time, and Tempo is described as having similar effects to Novacoke and being a hallucinogen, making you disoriented, and the astral sight effect is described as "fleeting flashes" of astral space and auras.
Long story short, your idea is valid, but Tempo is so hard to get now, and fucks you up so much, that you could never use it to gain any useful experience of what it's like to be able to have astral perception.