You can still do this today, and it still works as well as it did back in the day. For an even more impressive trick use a razorblade as your rectifier, a toilet roll for the tuning capacitor, another toilet roll for the coil. Haven't found a low-tech way to make a piezo earphone just yet, but this gets the list of ingredients down to a jam-jar, a couple of toilet rolls, some insulated wire, an old razorblade, a bit of aluminum foil, some cardboard, that piezo earphone and a 100K or so resistor. Pure magic that such a list of parts can function as a radio, and without any power source other than the transmitter itself.