From 1874 Otto Lilienthal and his brother Gustav made systematic measurements of the lift on flat and curved surfaces. They used a rotating apparatus they had built themselves. In 1889 Otto Lilienthal published his book Der Vogelflug als Grundlage der Fliegekunst, Bird Flight as the Basis of Aviation. Today it is regarded as the most important publication on flight technology of the 19th century. After jumps from a springboard in his garden, he began real gliding flights only in the spring of 1891, from a disused sand pit near Derwitz in Brandenburg. On 9 August 1896 he crashed from a height of about 15 meters, and he died the next day.
His grave carries the sentence Opfer müssen gebracht werden, sacrifices must be made. It is often quoted as his last words. But the inscription was added only in 1940, and German Wikipedia considers it unlikely that these were his last words.