You mean prior to 1940? (a lot used in Bombs)
1950s (Russian) 8.5mm x 43mm
(better versions in late 50s and 1960s. Family production till 1991)
1959 Usable as Triode 5.5mm x 28mm
Similar Russian 6.5 x 25mm
(Family production till about 1971). Versions in Korean war
a similar size used in WWII bomb proximity fuses. One RAF raid would use up 250,000 sub-miniature tubes, a miniaturised version of 1T4 etc.
Regular mains Radio valves about 3W for the heater. By late 1950s sub-miniature military types only used 14mW for the filament heater and could use 22V HT.
Early post WWII hearing aids used valves based on the WWII sub-miniature types for proximity fuses and same size as a 1953 transistor. 0.7V filament to power two in series of 1.4V silver cell and HT a miniature 22.5V battery about same size as PP3