Bacon, the scientist, put forward a theory of thin copper globes filled with liquid fire, which would soar.

Leonardo, artist, studied the wings of birds.

The Jesuit Francisco Lana, in 1670, working on Bacon's theory sketched an airship made of four copper balls with a skiff attached; this machine was to soar by means of the lighter-than-air globes and to be navigated aloft by oars and sails.
But while philosophers in their libraries were designing airships on paper and propounding their theories, venturesome men, "crawling, but pestered with the thought of wings," were making pinions of various fabrics and trying them upon the wind.

Four years after Lana suggested his airship with balls and oars, Besnier, a French locksmith, made a flying machine of four collapsible planes like book covers suspended on rods.

With a rod over each shoulder, and moving the two front planes with his arms and the two back ones by his feet, Besnier gave exhibitions of gliding from a height to the earth.