Theory:
1. A sigil represents a particular set of instructions encoded in abstract symbols that are sent to the subconscious, which then carries out those instructions.
2. Drugs such as THC operate by stimulating certain receptors in the brain, prompting certain electrochemical states to arise. This can be thought of as chemical delivery of instructions to the subconscious which the brain then must then carry out.
Ergo 3. It ought to be possible to encode into a sigil the instruction to recreate a particular electrochemical brain-state, and deliver it to the subconscious such that that brain-state can be re-achieved without further use of chemical prompting.
tl;dr smoke weed, get high. make high into sigil. use sigil to get high again later.