Samuel Ball Platner, Thomas Ashby, A Topographical Dictionary of Ancient Rome

PULVINAR SOLIS:

apparently a sort of an annex to a temple or shrine of the Sun, or possibly the shrine itself, situated near the temple of Quirinus on the Quirinal. It contained an inscription relating to the evening star, Vesperugo (Quint. i. 7. 12), an evidence of Greek influence that puts the erection of the shrine not earlier than the third century B.C. The day of dedication was 9th August (Hemerol. Capran. Amit., CIL i². p. 324), and the exact site is unknown. C. F. Hermann's emendation of Varro, LL v. 52, by which Solis pulvinar is read in the list of ARGEI (q.v.), is very doubtful (HJ 406, WR 316; Rosch. iv. 1140).