One of the constant features in synagogue architecture is the eternal flame (ner tamid in Hebrew). This lamp, now normally hung in front of the Ark which holds the torah scrolls at the eastern end of the synagogue, is the fulfillment of the instruction in Exodus XXVII:

And thou shalt command the children of Israel, that they bring thee pure olive oil beaten for the light, to cause the lamp to burn always. In the tabernacle of the congregation without the vail, which is before the testimony, Aaron and his sons shall order it from evening to morning before the Lord: it shall be a statute for ever unto their generations on the behalf of the children of Israel.

The lamp assumed a further role in Jewish lore in legends following the Hasmonean revolt. According to the Talmud (Tractate Shabbat, 21) the triumphant Jews on regaining possession of the Temple after the revolt found that the departing Seleucid forces had defiled all the oil for the lamps, save for a single barrel. By a miracle this barrel lasted out a whole eight days until 'kosher' oil could be obtained, and this was origin of the Jewish 'festival of lights', Chanukah. The memorial lamp at Chanukah is normally in the form of an eight-branched candelabrum or Menorah, although the traditional menorah of the Temple and used as a symbol of the Jewish people is seven-branched. The great Menorah of the Temple was seized by the Romans and transported to Rome, as famously depicted on the Arch of Titus. The modern ner tamid, its remote descendant, is however a single light, and powered by electricity or gas.

Semper's design for the Dresden ner tamid (right, in an illustration from the Vienna 'Allgemeine Bauzeitung' of 1847) is a renaissance-style interpretation of the traditional lamp. This is undoubtedly the lamp of which Cosima Wagner commissioned a copy (see next section). The archives of the Zurich ETH contain two drawings by Semper relating to the Dresden ner tamid, both apparently at the half-size scale of the sketch sent to Nietzsche. One drawing (on paper) dates from the time of the original synagogue building and corresponds to the 1847 illustration shown here; the second (on tracing paper) gives only outlines of the lamp's decoration (on the left-hand side only). It is possible that this second drawing may relate to the enquiry by Nietzsche (information from ETH).