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.

In his journal page for January 31, 1962, Indiana records that he had no class today (at Scarsdale, where he taught art classes), so he spent a considerable portion of the day working on his Polygon series. The page includes a sketch of Triangle. Indiana painted two versions of this painting, Polygon: Triangle) and Tintinnabulation; the latter went to Mr. and Mrs. Irving Castle, as indicated by a note added at a later date. He also notes that he received a call from Rosa Esman (of the Tanglewood Gallery), who confirmed that she and her husband wanted to keep Andabatarianism (Made in USA) and Gog, one for the dining room and the other for the living room.

Indiana then records going out for supplies and magazines, writing that Jim Dine made the current issue of Time, and that the magazine was "not too greatly impressed" by his work. He notes having veal cutlets for dinner, and then working into the morning on the Polygons, "still not getting much painting done in [this] department."