Leonardo studied mechanical wings for a long time and this is a reconstruction of one of the many projects for a flying machine documented in Manuscript B.
In his fascination with flying, Leonardo attempts to combine the dynamic potential of the human body with an imitation of natural flight. In his notes, he cites the bats, the kite and other birds as models to imitate. He refers to his flying machine as the “great bird”.
An object offers as much resistance to the air as the air does to the object. You may see that the beating of its wings against the air supports a heavy eagle in the highest and rarest atmosphere, close to the sphere of elemental fire. Again you may see the air in motion over the sea, fill the swelling sails and drive heavily laden ships. From these instances, and the reasons given, a man with wings large enough and duly connected might learn to overcome the resistance of the air, and by conquering it, succeed in subjugating it and rising above it.— Leonardo