The message on the card addressed to Mrs. Louise Perry at Dr. Sahler's Sanitarium reads:
I expect to be at the Sanitarium next Sunday and shall be so glad to see you. Please tell Myra Powers I am coming
cordially E. Hathaway
The story of Dr. Sahler's Sanitarium is probably more interesting than the postcard itself. Dr. Sahler, who was educated at Columbia, was also an expert in the occult. An advertisement in a 1901 edition of the Metaphysical Magazine: a monthly review of the occult sciences, included this clip on the sanitarium:
Dr. Sahler also received a glowing assessment in the Phrenological Journal and Science of Health, volume 109, 1900. Phrenology, according to Wikipedia, "is a pseudoscience primarily focused on measurements of the human skull, based on the concept that the brain is the organ of the mind, and that certain brain areas have localized, specific functions or modules." Phrenologists would measure the skull and feel the bumps in the skull to assess personality traits.
Dr. Sahler also worked with mediums and auras, as reported in the Journal of the American Society for Psychical Research (1909). Here's an excerpt:
I only wish that Louise Perry could tell us about her experiences at the Sanitarium.