The Emirates A380 has a shower unit for use by First class passengers (previously discussed here), but it got me thinking about the many passenger comforts present in the "golden age" of aviation (pre-US airline industry deregulation, especially when piano lounges were a thing in 747 aircraft) - did any other commercial passenger aircraft (jets or otherwise) have onboard showers for the benefit of passengers?
If not, it seems surprising, because a toilet room could easily be converted to a wet-room shower unit - and aircraft have a ready supply of potable water. Showers could be time-limited to a few minutes - enough to freshen-up after a long-haul flight and I can see it would be popular with business travelers who might not have the luxury of time to use their airlines' business class lounge's showers.