It's quite possible that Tesla's Pierce-Arrow is an inverted A/C single phase induction motor. Inverted in the sense that, instead of 120V at 60 Hz feeding a voltage coil of many turns of thin wire wrapped around a bobbin positioned on the armature surrounding the squirrel cage of modern day motors, he may have fed 1Meg Hz of very low voltage (gathered from the aerial atop the backside of the car) to the pair of stout copper wires wrapped around (and through) the laminations of a single-phase, A/C induction motor expecting to induce high voltage, low current in its voltage coil/s. Using the schematic, presented here and simulated in Micro Cap, it's possible to speculate how simple was his setup!...

The project box would have merely contained a HF sinewave generator. Since it's directly connected to the current coils of the A/C motor (not its voltage coil), the 1Meg Hz (or thereabouts) sinewave must pass through heavy cable (on its way to the front of the car) and offer as little resistance as possible to the massive current of low voltage traveling through it. The low voltage of these heavy cables supplies what little is needed to power this sinewave generator. This low voltage is sourced from the aerial on the backside of the car (according to what my simulation is suggesting).

Additionally, the A/C motor would have had to been custom made to handle HF. Motors of today boast being developed for several thousand Hz to power hybrids. Since my simulation is merely a suggestion of what may be required to make this a successful venture, it's possible that I've overshot bare minimums?