It's my first time in the Philosophy section of Stack Exchange. Since I am a non-native speaker, normally I ask questions in English Language Learners. However, I thought this one was in the field of philosophy, rather than language. So here I am.
My question is a quote from God is not Great by Christopher Hitchens.
... on the whole, the instruction was innocuous. Or it would have been, if not for a sign at the entrance to the Bhagwan’s preaching-tent. This little sign never failed to irritate me. It read: “Shoes and minds must be left at the gate.” There was a pile of shoes and sandals next to it, and in my transcendent condition I could almost picture a heap of abandoned and empty mentalities to round out this literally mindless little motto. I even attempted a brief parody of a Zen koan: “What is the reflection of a mind discarded?”
As I stated above, I am a non-native and not sure if I get the full meaning(s) of the word reflection in this context. It might mean "the sound of the thing thrown away", or "the deep thoughts on a matter" as well. As a result of failing to determine the appropriate meaning of the word reflection, I can't come up with a solid meaning of the whole sentence.
As Hitchens said, it is a koan. So (I think) it must be catchy and hint at something worth considering. Yet again, as Hitchens said, it is a parody of koan. So it may not mean anything so deep at all. However, if I know Hitchens' style, he certainly makes an important if slight point here. That is why I am not asking the question in ELL site but in here. I want to know the full meaning (if any) beyond the literal meaning of the sentence.
Long story short, I am confused in every aspect. I would greatly appreciate any kind of help.