Founded by Giovanni, cardinal bishop of Porto e Saint Rufino as a Cistercian daughter house of the (male?) monastery of Casae novae, in 1273 (see "miscellaneous info," below).
1292: Pope Nicholas IV gives papal exemption: census (tax) is a pound of wax for each year since the foundation stone was laid; In 1298, Pope Boniface VIII condedes certain privileges
[1] 1273: Papal letter of confirmation; [2] 1292: privileges of Pope Nicholas IV
Taxa S. Cancellariae Romanae in lucem emissa et notis illustrata;
Thesaurus novus anecdotorum., vol. IV, St. XIII, a. 1273
Originum Cisterceinsium, vol. 1;
Vita della Beata Angelina de Corbara, p. 203
Around the same time that this community was founded, Giovanni, cardinal bishop of Porto e Saint Rufino also had a number of other communities incorporated as daughter houses of the Cistercian order (see records #S. Trinità, S. Pancrazio sulla Via Aurelia, al Gianicolo). It may be that S. Tommaso had also had an earlier existence, and the 1273 was not a foundation date, but the date of their incorporation into the Cistercian order. Needs verification.