If it is a body that is so gifted in talents such as yours, Reimu-san,I will give you love until you rot away.That is more than enough time to obtain your corpse.You will be asleep for some tens of minutes only, but then...That cloth was soaked in the external alchemy (wàidān) of the arts of sleeping (wògōng).
wàidān is apparently external alchemy of Taoist alchemy. As for wògōng, I'm not too sure, but it's apparently related to qigong and the arts of lying down/sleeping, I think.