Volapük is one of the many attempts of making a universal, easy to learn language. It was created by Johann Martin Schleyer in 1879-1880. And abandoned in the early 1900’s. According to Wikipedia there are now an estimated 20-30 Volapük speakers in the world. If that’s correct, this is pretty amazing:
The Volapük Edition of Wikipedia has more than 100 000 articles.
Now that’s some productive 20-30 persons!