Regiomontanus and the eagle that he is said to have constructed to
accompany Charles V. on his entry into Nuremberg. In fact, Lana starts
his work with a study of the pioneers of mechanical flying up to his
own time, and then outlines his own devices for the construction of
mechanical birds before proceeding to detail the construction of the
aerial ship. Concerning primary experiments for this he says:--

'I will, first of all, presuppose that air has weight owing to the
vapours and halations which ascend from the earth and seas to a height
of many miles and surround the whole of our terraqueous globe; and this
fact will not be denied by philosophers, even by those who may have but
a superficial knowledge, because it can be proven by exhausting, if
not all, at any rate the greater part of, the air contained in a glass
vessel, which, if weighed before and after the air has been exhausted,
will be found materially reduced in weight. Then I found out how much
the air weighed in itself in the following manner. I procured a large
vessel of glass, whose neck could be closed or opened by means of a tap,
and holding it open I warmed it over a fire, so that the air inside it
becoming rarified, the major part was forced out; then quickly shutting
the tap to prevent the re-entry I weighed it; which done, I plunged its
neck in water, resting the whole of the vessel on the surface of the
water, then on opening the tap the water rose in the vessel and filled
the greater part of it. I lifted the neck out of the water, released the
water contained in the vessel, and measured and weighed its quantity and
density, by which I inferred that a certain quantity of air had come out
of the vessel equal in bulk to the quantity of water which had entered
to refill the portion abandoned by the air. I again weighed the vessel,
after I had first of all well dried it free of all moisture, and found
it weighed one ounce more whilst it was full of air than when it was
exhausted of the greater part, so that what it weighed more was a
quantity of air equal in volume to the water which took its place. The
water weighed 640 ounces, so I concluded that the weight of air compared
with that of water was 1 to 640--that is to say, as the water which
filled the vessel weighed 640 ounces, so the air which filled the same
vessel weighed one ounce.'

Having thus detailed the method of exhausting air from a vessel, Lana
goes on to assume that any large vessel can