alternate astable multi vibrator design
An astable multivibrator consists of two amplifying stages cross-connected in a positive feedback loop along with two RC coupling networks.  Therefore it requires active components such as BJTs or MOSFETs, and canot be made from just a combination of passive components such as resistors and capacitors.

This is about as simple as it gets (classic astable circuit):



The active elements (BJTs or whatever) are required to control the alternate charging and discharging of the capacitors that (along with their associated resistors) control the period of the oscillation.  Carefully read the Operation section in the article you linked to for more information.