FROM CARD: "QUIPU. SEE PUBLISHED INFORMATION. WM. M. GABB, ON INDIAN TRIBES AND LANGUAGES OF COSTA RICA. PP. 483-602 IN VOL. 14, 1875 OF THE PROCEEDINGS OF THE AMERICAN PHILOSOPHICAL SOCIETY, PHILADELPHIA, ESP. PAGES. 491-492."
As per the citation on the catalogue card, here is an excerpt from pp. 491-492 of Gabb, William M. On the Indian Tribes and Languages of Costa Rica. Proc. American Philos. Soc, XIV, 1876: "During my travels in Talamanca I collected in each district an accurate enumeration of the population. My process was to get together several of the most intelligent and well-informed men in the district; cause them to compare notes and then to tie a series of knots in strings as they are accustomed to do; different kinds of knots distinguishing the sexes. Each house was counted separately, so that I obtained an exact census of the whole country with the following results. This cord census is now in the museum of the Smithsonian Institution, with many other articles, illustrating the life and customs of the people." (The passage then continues with a list of the results of the census.) This publication is available online; here is a link to it starting at p. 491: http://biodiversitylibrary.org/page/31206016 .
Additional general reference: Gabb, William M. Informe sobre la exploración de Talamanca :verificada durante los años de 1873-74. San José de Costa Rica, A.C. : Tip. Nacional, 1894.
A very detailed analysis: Splitstoser, J. 2022. A Comparison of Two Knotted-Cord Fabrics: An Inca Khipu and a Costa Rican Census. Textile Museum Journal. 49. p 136 - 157