On the 10th of August 1763, the Mozart travelled on the market ship from Mainz to Frankfurt. They had left some of their luggage behind in Mainz. Frankfurt was only meant to be a short trip.They ended up staying three weeks. On the banks of the Main, the enormous cranes with which the goods were hoisted onto land immediately struck them. These «drones» were worth an entry into Leopold’s travel diary.Two such cranes can be seen on the Merian city map of 1761. The painter, Friedrich Wilhelm Hirt recorded one of them in his view of the Mainkai in 1757. On the inside of the cranes, there was a large tread wheel that was kept going by labourers.