Carlos S. Alvarado, PhD, Research Fellow, Parapsychology Foundation
Here are some important books about experimental ESP studies published between 1930 and 1958 that are freely available online.

Whateley Carington
Humphrey, B.M. (1948). Handbook of Tests in Parapsychology. Durham, NC: Parapsychology Laboratory.
Pratt, J.G., et al. (1940). Extra-Sensory Perception After Sixty Years. New York: Henry Holt.
Rhine, J.B. (1935). Extra-Sensory Perception. Boston Bruce Humphries. (First published in 1934)

J.B. Rhine

J.G. Pratt

Gertrude Schmeidler

Robert McConnell
Sinclair, U. (1930). Mental Radio. Pasadena, CA: Author.

Upton Sinclair

Mary Craig Sinclair Upton’s wife, tested for telepathy

Results of telepathy drawing test
Soal, S.G., & Bateman, F. (1954). Modern Experiments in Telepathy. New Haven: Yale University Press.
Warcollier, R. (1938). Experimental Telepathy. Boston: Boston Society for Psychic Research.

René Warcollier
Telepathic Drawing Experiments (Target Above, Response Below)