The Historia Augusta is a collection of biographies of emperors between 117-284. The author or authors are unknown but the date of composition is generally believed to be at the end of the 4th century. The trustworthiness is a major problem, but unfortunately it is often the only source. I have no clue if the following anecdote is true, but as the Italians say: se non è vero, è ben trovato.
Emperor Hadrian (117-138) used to go bathing in a public bath house. At one of these visits he sees there a veteran known to him, who rubs is back against the marble wall. Generous as he is, Hadrian gives a slave to the man for rubbing him. The next time when he visits the bath house, there are numerous old men rubbing their backs against the marble walls...
Historia Augusta, Hadrianus, 17, 5-7:
5 Omnes reges muneribus suis vicit. Publice frequenter et cum omnibus lavit. 6 Ex quo ille iocus balnearis innotuit : nam cum quodam tempore veteranum quendam notum sibi in militia dorsum et ceteram partem corporis vidisset adterere parieti, percontatus, cur se marmoribus destringendum daret, ubi audivit hoc idcirco fieri, quod servum non haberet, et servis eum donavit et sumptibus. 7 Verum alia die cum plures senes ad provocandam liberalitatem principis parieti se adtererent, evocari eos iussit et alium ab alio invicem defricari.
munus muneris (n.): gift
vicit: i.e. Hadrianus
vinco vici victum: to surpass someone (acc.) in (abl.)
balnearis – e: pertaining to a bath (iocus balnearis: bathing joke
innotesco innotui: to become famous
notum sibi in militia: known to him from the army
adtero adtrivi adtritum: to rub
paries parietis (m.): wall
perconto: to ask
cur se marmoribus destringendum daret: why he gave himself unclothed (litt. `having to be unclothed’) to the marble
idcirco: for that reason
sumptus -us (m.): money for covering expenditures
ad provocandam liberalitatem principis: for appealing to the generosity of the emperor
invicem: in turn
defrico defricui defricatum: to rub hard