1. Rosen, op. cit. (ref. 3), 175. See also Biskup Marian, Regesta Copernicana (Studia Copernicana, viii; Wroclaw, 1978), 63, no. 91; and Hajdukiewicz Ludwik, Biblioteka Macieja z Miechowa (Wroclaw, 1960), 205 and 218. The date of the entry is 1 May 1514.
2. This was the view maintained by Birkenmajer Antoni Ludwik: Mikotaj Kopernik (Cracow, 1900), 166. See Biskup, Regesta (ref. 4), 65–66, items 98 and 102. The observation is dated 11 March 1515; note that the second in 1516 was the result of a calculation, not an observation. Swerdlow, “Derivation” (ref. 1), 430, points out that Copernicus could not have derived the motion of the Earth's apsidal line as presented in De revolutionibus until 1522 or 1524, but that is compatible with the weaker claim that around 1515 Copernicus began to doubt his assumption in Commentariolus.