Wednesday, Aug. 22 On Nevada de Toluca
Rode to crater & visited lake.... A rounded hill in the midst of the crater is said to be a Pelee spine.... Climbed to the highest point more than 15,000 ft. Very little snow.... Popocataypital [sic Popocateptl] partly cloud hidden. Nevada de Toluca is the 4th in height of the Mexican volcanoes.
— Notebook 42, 1906, [pages 162 – 163]