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 entry for December 30, 1962, Indiana records that it was a "beautiful crisp day, sunny and cold, particularly in [the] loft, as I forgot to close [the] damper on my potbelly, and I had only a bed of cold ash when I got up [this] morning." He writes:

"The two sets of newly born polygons [Small Black Diamond Polychrome Numeral Quartet Summing Thirty and Four Numbers Summing 30] look v[ery] good in [the] natural light of day: no regrets, but eager [to] begin [the] third set, where [the] polychromy might verge more on monochromy."

Indiana then notes mopping down the stairway, wanting the mop to be in good shape for the New Year, and putting the final touches on Mate, which was being picked up by Howard Lipman (who purchased the sculpture), and would be visiting the loft for the first time. 

The entry also includes a sketch of a diamond painting with the number eight, with the note "another 4-piece set."