“It is advisable to protect the crown of the head from the direct action of the sun’s rays. Therefore, yogis put up their hair in a knot on the crown of their heads. Besides the heat, the sun’s rays contain certain “chemism” which, during the periods of increase of sunspots, may be harmful. In general, during the opening of the centers one should avoid direct contact with the sun’s rays. Excessive physical exercises, such as sports, are also quite harmful. (28 August 1931)”