This was surprisingly difficult to find information on.
Translated by yours truly: The border line covers the territory between the mouth of the Yavarí river and the mouth of the Yaverija river in Acre (Brasil) and extends entirely en the Amazon Jungle. [...] The border was demarcated two treaties: Convención Fluvial sobre Comercio y Navegación entre la República del Perú y el Imperio del Brasil which creates the north border at the beginning of the Yavarí and the Tratado de Límites, Comercio y Navegación de la Cuenca del Amazonas, entre el Perú y Brasil. I couldn't find an English source for either treaty nor do I really feel like translating five pages lol. I guess it follows the Yavarí for most of the way until it meets the Río Branco? Not sure where it goes from there though
I wouldn't trust any count. By definition, we don't know them very well, and you need a certain level of cultural insight to pick apart ethnic groups that are all rainforest hunter-gatherers.
This map still reflects the crazy daring of both:
"Fitzcarraldo" as the main character in the film.
"Fitzcarraldo" as the Werner Herzog on-location film production.
They hated each other, were constantly fighting to the point Kinsky almost killed Herzog but they still shot 5 movies together in the most impossible locations.
At one point one of the native chief they were working with offered to kill Hinsky. Herzog declined the offer because he still needed the Hinsky to finish the movie.
For Fitzcarraldo they bought 3 similar 320 tons steamboat. They actually pulled the boat uphill manually without any special effects. Then in the scene were the boat crashed in the rapid they actually crashed the boat on rapid while filming inside. Half of the people involved in the filming of this sequence ended up injured.
Two plane crashed during the movie .... Honestly I fell like what happened behind the scenes of the movie is even more fascinating and dramatic than the movie itself.