See Semahot VIII, 7, and S. Lieberman, “Some Aspects of Afterlife in Rabbinical Literature,” American Academy for Jewish Research 1965, I, pp. 495–532. On p. 509, “Since there is no doubt that it was permitted to place the personal belongings of the deceased beside his body, not because he is in need of them, but because the sin arouses the grief of the onlookers.”