"The sailing flight of birds is the only form of flight which is carried on for some length of time without the expenditure of power."

“The contrivances which are necessary to counteract the wind effects can only be understood by actual practice in the wind.”

“The increasing size of the apparatus makes the construction more difficult in securing lightness in the machine; therefore the building of small apparatus is to be recommended.”

“The supporting powers of time air and of the wind depend on the shape of the surfaces used, and the best forms can only be evolved by free flight through the air.”

“Lilienthal's appendix from Chanute's book Progress in Flying Machines”

“The difficulty of rising into the air increases rapidly with the size of the apparatus. The uplifting of a single person, therefore, is more easily attained than that of a large flying machine loaded with several persons.”

“The maintenance of equilibrium in forward flight is a matter of practice, and can only be learned by repeated personal experiment.”