many are mention-y, or not independent of Humboldt
1821, Alexander von Humboldt, Aimé Bonpland, Personal Narrative of Travels to the Equinoctial Regions, v. 5, pt. 1, page 231:
Here we saw for the first time that white and fungous substance, which I have made known by the name of dapicho and zapis. We [...thought] the dapicho was a fossil cauotchouc, though different from the elastic bitumen of Derbyshire. A Poimisano Indian, seated by the fire, in the hut of the missionary, was employed in reducing the dapicho into black caoutchouc.
1848, Pharmaceutical Journal: A Weekly Record of Pharmacy and Allied Sciences, page 272:
Humboldt witnessed the process for obtaining both the dapicho and the commercial caoutchouc, and his account is so interesting, and abounds in so many valuable suggestions, that notwithstanding its length, I trust I shall be pardoned for giving an extract […]
1851, William Macgillivray, The travels and researches of Alexander von Humboldt, page 224:
[...] the old Indian who accompanied them showed that it was obtained by digging several feet deep among the roots of two particular trees, the Hevea of Aublet and one with pinnate leaves. This substance, which bears the name of dapicho, is white, corky, and brittle, with a laminated structure and undulating edges; but on being roasted it assumes a black colour, and acquires the properties of caoutchouc.
[Humboldt] then observed that, to procure the dapicho, it was necessary to dig to the depth of three or four feet, in marshy ground, between the roots of two trees, known by the name of Jacio and Cursana. […] We observe that dapicho is the result of an exudation of vegetable juices from the roots of trees, and, notwithstanding the uniformity of temperature, the trees of the torrid zone experience in the round of vegetation, periodical changes; that effusion is consequently pretty regular.
