Reddit mentions of The Pamirs; Being a Narrative of a Year's Expedition on Horseback and on Foot through Kashmir, Western Tibet, Chinese Tartary and Russian Central Asia: Volume 2

I got it from this book here, though I lifted the body of the quote from the Wikipedia article on historical Khotan.

It's a work by the 7th Earl Dunmore recounting his travels in Central Asia and is certainly a product of its time period, reflecting many of the culture mores, biases, and prejudices typical of 19th century Western visitors to foreign lands. It details the author's perception of how things were in Khotan, though the degree to which this perception reflected actual reality may be subject to debate.

That said, I mainly included the point to emphasize the fact that Khotan in the 19th century was of relatively minimal regional import (such that courtesanship, as opposed to some other economic or political contribution, was its major claim to fame/notoriety) and to juxtapose it against Paris's cosmopolitan reach and comparative global importance.