The Heptagram of the Seven days is a particularly interesting way to view the order of the celestial bodies. If reading clockwise from the top-most symbol, it is the order of the planets from the Geo-centric Qabalistic model: Saturn, Jupiter, Mars, Sol, Venus, Mercury, Luna. If read following the lines of the Heptagram, one gets the days of the week: Saturday (Saturn’s Day), Sunday (Sun’s Day), Monday (Moon’s Day), Tuesday (Tiw’s Day, Norse War God), Wednesday (Wodin’s Day), Thursday (Thor’s Day), Friday (Frigga’s Day, Norse Love God.) 

Crowley attributes this realization to Frater Deo Duce Comite Ferro, S.L. MacGregor Mathers. 

This is one of two different kinds of Heptagrams. This version is known as 7/3 Heptagram, as each line connects the planet that is three planets away. The other version of the Heptagram is called a 7/2 Heptagram, and is used for the Seal of A∴A∴