"Faster still the two troikas flew"
A Russian Troika
Public DomainA Russian Troika

 This can be read as a reference to Nikolai Gogol's novel Dead Souls, published in 1842. In a famous passage in this novel Gogol compares Russia to a troika: "And you, Russia of mine--are not you also speeding like a troika which nought can overtake? Is not the road smoking beneath your wheels, and the bridges thundering as you cross them, and everything being left in the rear, and the spectators, struck with the portent, halting to wonder whether you be not a thunderbolt launched from heaven?"

A troika is a Russian harnessing system used to pull a carriage or sleigh with three horses side by side.