Attached is an image of the Eastman watercolor, which I copied from the book Seth Eastman: A Portfolio of North American Indians, by Sarah Boehme, and Patricia Johnston (Afton, MN, 1995). The painting in question is illustrated on page 116.
The caption accompanying the painting reads in part: “In addition to seven mounds (‘Celtiberic tumuli,’ as he called them) and traces of ‘circumvallation,’ Schoolcraft located ‘on rising the hills to Parr’s Point … quite entire and undisturbed, the ruins of a tower or look-out, upon a commanding point of ground on the farm of Mr. Micheltree.’ It had been built over an excavation of several feet deep, walled with rough stones, and had supposedly once stood ‘many feet’ high. Similar remains were discovered by Schoolcraft on the other side of the Ohio River (Schoolcraft 1851-1857, 1: 123; see Squier and Davis 1848: 182).
“In Eastman’s view, which faces nearly due south, the conical appears in the distance behind scattered farmhouses and close to a bend in the Ohio River.” The caption is on page 117.
The watercolor drawing measures 4-15/16” x 7-5/8”
Something like this was also mentioned here.