In Henry J. Wehman’s The Mystery of Love, Courtship and Marriage Explained
(1890)
[https://archive.org/details/TheMysteryOfLoveCourtshipAndMarriageExplained/page/n33/mode/2up]
there are charts of secret messages Victorian flirters could send with fans,
parasols, gloves, and handkerchiefs.
Whether the handkerchief codes were ever in use (or mainly used
![Post-human flirting](/content/images/size/w795/image/fetch/w_1200-c_limit-f_jpg-q_auto:good-fl_progressive:steep/https-3A-2F-2Fbucketeer-e05bbc84-baa3-437e-9518-adb32be77984.s3.amazonaws.com-2Fpublic-2Fimages-2F538ac8c4-2eb3-4236-b613-954bdf69632d_1195x371.png)