Probably as an acclamatio; note palm is perpendicular to the ground and thumb is sticking up cf. Graham Sumner, Roman military clothing: 100 BC – AD 200, Oxford 2002, p. 47, pl. G3 (Diogmitoi [sic! correct plural: diogmitai]). نسخة محفوظة 2016-05-13 على موقع واي باك مشين.
It is unknown if Octavian's specific oath salute was a pre-existing Roman custom or if he modified a similar pledging gesture for his contio, but Cicero clearly disapproved of Octavian's performance, exclaiming: "I don't want to be saved by such a man"; cf. Cic. Att.16.15.3.6: Quamquam enim †postea† in praesentia belle iste puer retundit Antonium, tamen exitum exspectare debemus. at quae contio! nam est missa mihi. iurat "ita sibi parentis honores consequi liceat" et simul dextram intendit ad statuam. μηδὲ σωθείην ὐπό γε τοιούτου! [Nec servatoribus istis!]نسخة محفوظة 2022-05-11 على موقع واي باك مشين.
It is unknown if Octavian's specific oath salute was a pre-existing Roman custom or if he modified a similar pledging gesture for his contio, but Cicero clearly disapproved of Octavian's performance, exclaiming: "I don't want to be saved by such a man"; cf. Cic. Att.16.15.3.6: Quamquam enim †postea† in praesentia belle iste puer retundit Antonium, tamen exitum exspectare debemus. at quae contio! nam est missa mihi. iurat "ita sibi parentis honores consequi liceat" et simul dextram intendit ad statuam. μηδὲ σωθείην ὐπό γε τοιούτου! [Nec servatoribus istis!]نسخة محفوظة 2022-05-11 على موقع واي باك مشين.
Probably as an acclamatio; note palm is perpendicular to the ground and thumb is sticking up cf. Graham Sumner, Roman military clothing: 100 BC – AD 200, Oxford 2002, p. 47, pl. G3 (Diogmitoi [sic! correct plural: diogmitai]). نسخة محفوظة 2016-05-13 على موقع واي باك مشين.