Dean

I would not call the first one a tank, but there was the Panzerkampfwagen Bar at 120 tons, and the Panzerkampfwagen Lowe, at a mere 90 tons.
I also found a reference to the Panzerkampfwagen E-100, which weighed in at 140 tons.

These were the more serious designs. In the "pure fantasy" category, there was the P-1000, which was supposed to weigh in at 1000 tons. However, later estimates would have put the actual weight closer to 2000 tons. It was supposed to have Graf Spee turrets with the centre gun removed.... hmmmm....!

Then, there was the P-1500 Monster, a 1500 ton, 800 mm self propelled gun. These are the fantasies that occur when non-military idjits end up taking over countries and are allowed to realize their military fantasies....

Dean