Yes, I remember reading that - though it was just a passage in one book in the "Orion" series (that series also had an idea about the "real" Noah's Ark - that it was seeds and plants collected and saved in a hurry from a valley just about to be flooded. That would be from an early attempt at plant domestication).

The "horse" part of the siege tower idea was that the towers would be protected against fire etc. by horse hides.

I have also heard it described as a boat.