Robert Indiana kept a series of illustrated journals during the late 1950s and 1960s, in which he discusses the development of his work as well as his daily life on Coenties Slip.

This journal page covers February 18–19, 1961. In his entry for February 18 (mistakenly dated January 18) Indiana records hearing "explosions" on the waterfront, which he learned later was the gun salute of the British HMS Ark Royal.  He notes that there was rain and fog, "a very London day," and that he spent it cleaning the loft.

The entry for February 19 (mistakenly dated January 19) is dominated by a sketch of The Sweet Mystery, with a note "add yellow." He also records "no word from Fulton Street," a reference to not having heard from Steve and Barbara Durkee, who lived there.