5AM, the twelfth hour of the night on a Sunday, belongs to Mercury. Mercury's hours were kept for communication, study and skilled craft: writing, teaching, contracts of business rather than land, travel, and divination itself, since Mercury was read as the planet nearest the working of the mind. The grimoire tradition treats Mercury as changeable, taking on something of the character of whatever planet stands nearest it. Practitioners were counseled to match the work to the hour wherever the two could be arranged together, choosing an hour whose ruling planet suited the operation in hand rather than acting in whatever hour happened to be free; a working that fit its planet well was held to draw strength from the hour, while one that fought the ruling planet's nature was held to labor against it.
Because the same planet returns roughly every seventh hour through the whole day, Mercury also rules 8AM, 3PM and 10PM elsewhere on this reference Sunday, so a practitioner without access to 5AM specifically could look to those instead for work of the same character. The hour sits inside a wider correspondence system built around the same seven planets: Mercury is paired with the metal an alloy standing in for quicksilver, mercury itself being liquid at ordinary temperature, with orange or a mix of colors, and with Wednesday, the weekday carrying its name in full as well as its first hour. A working timed to 5AM was traditionally strengthened further by choosing Wednesday itself and by using that metal and color in the object the working required, and the same logic timed ordinary practical acts as well as ritual, from gathering herbs held sacred to a planet to medical treatments believed to answer best to its temperament.