On Sep. 1, Sikhs will celebrate the 400th anniversary of the day their holy book was first brought to their most sacred site. In 1604, Guru Arjan Dev carried the Guru Granth Sahib into the Golden Temple in Amritsar, Punjab. The book is accorded such respect that a prayer is spoken before the book is closed, and it’s swaddled in fine cloth and carried on the head.

India’s prime minister, Manmohan Singh, the first Sikh to hold that post, will preside over the 4 million-strong celebration. In a nod to modernity, Amritsar will host a laser show, very apropos since the inventor of fiber optics is a Sikh.

Every celebration has its inevitable drama. Due to tensions dating back to Indira Gandhi’s reign, Gandhi’s daughter-in-law Sonia Gandhi was not invited to the celebration. And a family which holds an even older copy of the holy book has yet to agree to put its copy on display:

The precious manuscript is kept in a 900-kg iron vault built by a German engineer. Though the family claims that the National Archives has preserved the pages, scholars are sceptic. Says Dhillon, “The preservation was done sometime in the 1960s by an outdated method. Nowadays the accepted practice to preserve such manuscripts is to get them microfilmed and as far as I know this has not been done.”

Nonetheless, Amritsar is being newly repainted, the temple walkways are getting new carpeting, and pilgrims are arriving by the trainload in anticipation of celebration.