Gustav Holst was born on 21 September 1874, under the sign of Virgo, ruled by the planet Mercury.

Mercury, as Holst would have read in his copy of Alan Leo's What Is a Horoscope and How Is It Cast?, is known as the “winged messenger of the gods,” and a favorable planet for those who have left the senses for the mind. It is a mutable planet, absorbing all with which it comes into contact. Since Holst's death in 1934, those who knew him and who have written about him have given witness – though perhaps unwittingly – to his Mercurian attributes. There is always accent upon his mental life; physically frail and prone to illness, he was indefatigable in his curiosity and intellectual flights. His was not a brilliant personality, making him once again, according to the descriptions in Leo's book, a typical Mercurian; nor was he ever interested, compositionally, in fluency and pyrotechnics for their own sake. Slow and plodding in his work habits, he was often criticized late in his life for lacking spontaneity, for being too mechanical and dry. Early in his professional career, he fell into school teaching – the young ladies at St. Paul's Girls' School and, at Morley College, the working class – as a way to support his family. And this daily school work may well have contributed to his methodical ways, and might have played a part in the development of a technique which found beauty and cleverness in simple musical devices.