Take some dry earth containing some plant life, grind it all up, put it into a pot, and collect enough rainwater to seal out any release of geosmin from the soil. Remove the plants after letting soak for ~4 hours. Cover with a lid. Boil at a high temperature for about an hour. Filter out and collect the muck. Repeat the boiler/filter process until the muck buildup is enough. Set to dry on a thin sheet. You now have petrichor. Boiling and filtering and drying can derive pretty much anything. Also, I’d say the rainwater and the specific timing prescribed in MS aren’t totally necessary. The cool refreshing smell (petrichor) you get after it rains is the acidity that releases the geosmin. This can also be done using hot water. There needs to be what chemistry calls a reagent (or maybe the term is ‘reacting agent’, I’m not sure on this one). The ‘muck’ that will be the incense however is not the barren plants that you remove, it’s the resin left over from boiling–that is, concentrated geosmin. When you light it the flame acts as the reagent and you thus produce petrichor.