On page 560 of the 1872 Monatsberichte der Königlich Preußischen Akademie der Wissenschaften zu Berlin (Monthly Reports of the Royal Prussian Academy of Science in Berlin), there is a brief mention that on 18 July, "Hr. Weierstrass las über stetige Funktionen ohne bestimmte Differentialquotienten" (Mr. Weierstrass read [a paper] about continuous functions without definite [i.e., well-defined] derivatives [to members of the Academy]). However, Weierstrass's paper was not published in the Monatsberichte.
See also: Karl Weierstrass, Abhandlungen aus der Functionenlehre [Treatises from the Theory of Functions] (Berlin, Germany: Julius Springer, 1886), page 97.
At least two researchers formulated continuous, nowhere differentiable functions before Weierstrass, but their findings were not published in their lifetimes.
Around 1831, Bernard Bolzano (1781–1848), a Czech mathematician, philosopher, and Catholic priest, constructed such a function; however, it was not published until 1922. See:
Martin Jašek (1922), "Funkce Bolzanova" (Bolzano's function), Časopis pro Pěstování Matematiky a Fyziky
Gerver, Joseph (1971). "More on the Differentiability of the Riemann Function". American Journal of Mathematics. 93 (1): 33–41. doi:10.2307/2373445. JSTOR2373445. S2CID124562827.
Gerver, Joseph (1971). "More on the Differentiability of the Riemann Function". American Journal of Mathematics. 93 (1): 33–41. doi:10.2307/2373445. JSTOR2373445. S2CID124562827.
Gerver, Joseph (1971). "More on the Differentiability of the Riemann Function". American Journal of Mathematics. 93 (1): 33–41. doi:10.2307/2373445. JSTOR2373445. S2CID124562827.
