Please read Alexey Sklyarenko's annotations on Pale Fire, Ada and other Nabokov works here.
In his poem about a miragarl ("mirage girl") quoted by Kinbote (in VN’s novel Pale Fire, 1962, Shade’s mad commentator who imagines that he is Charles the Beloved, the last self-exiled king of Zembla) in his commentary the society poet and sculptor Arnor mentions a dream king in the sandy wastes of time and three hundred camels: